Add release notes.

Author: Jeff Verkoeyen

CHANGELOG.md

@@ -1,5 +1,14 @@
-# #develop#
+# 1.0.0
 
- TODO: Enumerate changes.
+Initial release.
 
+Includes support for building simple view controller transitions and transitions that support custom presentation.
 
+## Source changes
+
+* [Clarify the docs for default modal presentation styles. (#4)](https://github.com/material-motion/transitioning-objc/commit/84c23e5f7c490e2a7d299cca6c4046ac4f368551) (featherless)
+* [Initial implementation. (#1)](https://github.com/material-motion/transitioning-objc/commit/c1b760455779226ebc9749e06e528d25a6b444bc) (featherless)
+
+## Non-source changes
+
+* [Simplify the frame calculation APIs in the example. (#5)](https://github.com/material-motion/transitioning-objc/commit/8688b045594ee38204744c7c644d4cce58165ec6) (featherless)