Add initial pass for creating review comments
Add unit, integration tests for create_review_comment
Add ReviewComment#reply and integration tests

Also, add a missing call to super that was causing me to worry. Without
calling BaseComment's _update_attributes method, ReviewComment was
missing several attributes that I knew it should have had. Took me
longer than I care to admit to catch that.
Add unit tests for ReviewComment#reply
Merge pull request #286 from sigmavirus24/1.0-review-comment

Add initial pass for creating review comments