Refs #64, adds a comments table to the database.
Refs #64, adds Comment model with unit tests.
Refs #64, adds missing documentation for Comment unit test.
Refs #64, adds add-comment API script with test.
Refs #64, fixes return value of add-comment API script.
Makes TestEnvironment->teardown() delete media files as well as the database.
Refs #64, adds delete-comment API script and test.
Refs #64, adds get-comments API script and test.
Merge pull request #65 from RyffProject/feature/comments

Add comments to posts.