Improve Python generation for several special forms (#798)

Remove code which generates an assignment to a name for `do*`, `let*`
and `letfn*` forms which should significantly reduce the number of
redundant assignments generated by the Basilisp compiler.

Fixes #799

Author: chrisrink10

CHANGELOG.md

@@ -18,7 +18,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  * Allow vars to be callable to adhere to Clojure conventions (#767)
  * Adjust input path compatibility in `basilisp.core/load` input path to be relative to the namespace or the root path (#782)
  * No longer warn on unused bindings when their name begins with `_` (#756)
- * Improve the Python generation for `do`, `if`, `let*`, and `letfn*` forms to avoid unnecessary extra assignments (#793, #794)
+ * Improve the Python generation for `do`, `if`, `let*`, and `letfn*` forms to avoid unnecessary extra assignments (#793, #794, #799)
+ * Generate Python classes for `deftype*` and `reify*` forms using modern `@attr.define`, `@attr.frozen`, and `@attr.field` APIs (#799)
 
 ### Fixed
  * Fix issue with `(count nil)` throwing an exception (#759)