The reviews unit tests are some of the oldest in the codebase, and
predated a lot of our modern best practices. This change goes through
and applies a bunch of changes, such as:

* Docstrings for classes
* Single quotes instead of double quotes
* Spacing between class docstring and members
* Private functions below public functions
* Removed period at the end of the sentence for unit test docstrings
* Unit test docstrings that mention the class/function
* Usage of "with" when using assertRaises

The review request issues test suite also moved into
test_review_request.py.

Unit tests pass.