Misc. formatting/wording fixes to changelog

**what is the change?:**
Thanks to the kind code review comments of @gaearon and @nhunzaker we
have
- removed the non-deterministic bold styling on some bullet points
- improved wording of the bullet points for portals, attribute whitelist
  changes, and server rendering changes
- Add note about error boundaries including a breaking change to error
  handling behavior.
- punctuation and capitalization fixes

**why make this change?:**
Clarity and correctness

**test plan:**
Visual inspection

**issue:**
facebook#8854

Author: flarnie

CHANGELOG.md

@@ -7,19 +7,17 @@
 
 ### New JS Environment Requirements
 
- * **React 16 depends on the collection types [Map](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map) and [Set](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set), as well as [requestAnimationFrame](https://developer.mozilla.org/en-US/docs/Web/API/window/requestAnimationFrame).** If you support older browsers and devices which may not yet provide these natively (eg <IE11), [you may want to include a polyfill](https://gist.github.com/gaearon/9a4d54653ae9c50af6c54b4e0e56b583).
+ * React 16 depends on the collection types [Map](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map) and [Set](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set), as well as [requestAnimationFrame](https://developer.mozilla.org/en-US/docs/Web/API/window/requestAnimationFrame). If you support older browsers and devices which may not yet provide these natively (e.g. <IE11), [you may want to include a polyfill](https://gist.github.com/gaearon/9a4d54653ae9c50af6c54b4e0e56b583).
 
 ### New Features
 * Components can now return arrays and strings from `render`. (Docs coming soon!)
-* **Improved error handling with introduction of "error boundaries".** [Error boundaries](https://facebook.github.io/react/blog/2017/07/26/error-handling-in-react-16.html) are React components that catch JavaScript errors anywhere in their child component tree, log those errors, and display a fallback UI instead of the component tree that crashed.
-* `ReactDOM.createPortal()` is official and stable
-  ([@gaearon](https://github.com/gaearon) in
-  [#10675](https://github.com/facebook/react/pull/10675))
+* Improved error handling with introduction of "error boundaries". [Error boundaries](https://facebook.github.io/react/blog/2017/07/26/error-handling-in-react-16.html) are React components that catch JavaScript errors anywhere in their child component tree, log those errors, and display a fallback UI instead of the component tree that crashed.
+* First-class support for declaratively rendering a subtree into another DOM node with `ReactDOM.createPortal()`. (Docs coming soon!)
 * Streaming mode for server side rendering is enabled with `ReactDOMServer.renderToNodeStream()` and `ReactDOMServer.renderToStaticNodeStream()`. ([@aickin](https://github.com/aickin) in [#10425](https://github.com/facebook/react/pull/10425), [#10044](https://github.com/facebook/react/pull/10044), [#10039](https://github.com/facebook/react/pull/10039), [#10024](https://github.com/facebook/react/pull/10024), [#9264](https://github.com/facebook/react/pull/9264), and others.)
-* Allow [passing some "unknown" attributes through to DOM components](https://facebook.github.io/react/blog/2017/09/08/dom-attributes-in-react-16.html) ([@nhunzaker](https://github.com/nhunzaker) in [#10385](https://github.com/facebook/react/pull/10385), [10564](https://github.com/facebook/react/pull/10564), [#10495](https://github.com/facebook/react/pull/10495) and others)
+* [React DOM now allows passing non-standard attributes].(https://facebook.github.io/react/blog/2017/09/08/dom-attributes-in-react-16.html) ([@nhunzaker](https://github.com/nhunzaker) in [#10385](https://github.com/facebook/react/pull/10385), [10564](https://github.com/facebook/react/pull/10564), [#10495](https://github.com/facebook/react/pull/10495) and others)
 
 ### Breaking Changes
-- **There are several changes to the behavior of scheduling and lifecycle methods:**
+- There are several changes to the behavior of scheduling and lifecycle methods:
   * `ReactDOM.render()` and `ReactDOM.unstable_renderIntoContainer()` now return `null` if called from inside a lifecycle method.
     * To work around this, you can either use [the new portal API](https://github.com/facebook/react/issues/10309#issuecomment-318433235) or [refs](https://github.com/facebook/react/issues/10309#issuecomment-318434635).
   * Minor changes to `setState` behavior:
@@ -32,20 +30,21 @@
   * `componentDidUpdate` lifecycle no longer receives `prevContext` param. ([@bvaughn](https://github.com/bvaughn) in [#8631](https://github.com/facebook/react/pull/8631))
   * Shallow renderer no longer calls `componentDidUpdate()` because DOM refs are not available. This also makes it consistent with `componentDidMount()` (which does not get called in previous versions either).
   * Shallow renderer does not implement `unstable_batchedUpdates()` anymore.
-- **The names and paths to the single-file browser builds have changed to emphasize the difference between development and production builds.** For example:
+- The names and paths to the single-file browser builds have changed to emphasize the difference between development and production builds. For example:
   - `react/dist/react.js` → `react/umd/react.development.js`
   - `react/dist/react.min.js` → `react/umd/react.production.min.js`
   - `react-dom/dist/react-dom.js` → `react-dom/umd/react-dom.development.js`
   - `react-dom/dist/react-dom.min.js` → `react-dom/umd/react-dom.production.min.js`
 * The server renderer has been completely rewritten, with some improvements:
-  * Server rendering does not use markup validation anymore, and instead tries its best to attach to existing DOM, warning about inconsistencies. And there is no data-reactid anymore.
+  * Server rendering does not use markup validation anymore, and instead tries its best to attach to existing DOM, warning about inconsistencies. It also doesn't use comments for empty components and data-reactid attributes on each node anymore.
   * Hydrating a server rendered container now has an explicit API. Use `ReactDOM.hydrate` instead of `ReactDOM.render` if you're reviving server rendered HTML. Keep using `ReactDOM.render` if you're just doing client-side rendering.
-* When "unknown" props are passed to DOM components, in some cases, React will now render them in the DOM. [See this post for more details.](https://facebook.github.io/react/blog/2017/09/08/dom-attributes-in-react-16.html) ([@nhunzaker](https://github.com/nhunzaker) in [#10385](https://github.com/facebook/react/pull/10385), [10564](https://github.com/facebook/react/pull/10564), [#10495](https://github.com/facebook/react/pull/10495) and others)
+* When "unknown" props are passed to DOM components, for valid values, React will now render them in the DOM. [See this post for more details.](https://facebook.github.io/react/blog/2017/09/08/dom-attributes-in-react-16.html) ([@nhunzaker](https://github.com/nhunzaker) in [#10385](https://github.com/facebook/react/pull/10385), [10564](https://github.com/facebook/react/pull/10564), [#10495](https://github.com/facebook/react/pull/10495) and others)
+* Errors in the render and lifecycle methods now unmount the component tree by default. To prevent this, add [error boundaries](https://facebook.github.io/react/blog/2017/07/26/error-handling-in-react-16.html) to the appropriate places in the UI.
 
-### Removed deprecations
+### Removed Deprecations
 
-- **There is no `react-with-addons.js` build anymore.** All compatible addons are published separately on npm, and have single-file browser versions if you need them.
-- **The deprecations introduced in 15.x have been removed from the core package.** `React.createClass` is now available as create-react-class, `React.PropTypes` as prop-types, `React.DOM` as react-dom-factories, react-addons-test-utils as react-dom/test-utils, and shallow renderer as react-test-renderer/shallow. See [15.5.0](https://facebook.github.io/react/blog/2017/04/07/react-v15.5.0.html) and [15.6.0](https://facebook.github.io/react/blog/2017/06/13/react-v15.6.0.html) blog posts for instructions on migrating code and automated codemods.
+- There is no `react-with-addons.js` build anymore. All compatible addons are published separately on npm, and have single-file browser versions if you need them.
+- The deprecations introduced in 15.x have been removed from the core package. `React.createClass` is now available as create-react-class, `React.PropTypes` as prop-types, `React.DOM` as react-dom-factories, react-addons-test-utils as react-dom/test-utils, and shallow renderer as react-test-renderer/shallow. See [15.5.0](https://facebook.github.io/react/blog/2017/04/07/react-v15.5.0.html) and [15.6.0](https://facebook.github.io/react/blog/2017/06/13/react-v15.6.0.html) blog posts for instructions on migrating code and automated codemods.
 
 </details>