Django-comments-tree

Another fix for pip import issue

Another fix for pip import issue

Fix build error from b3

Migrate methods from __init__.py of django-contrib-comments.
These had been missed from previous migrations.

* change method used for version, since previous one failed on install.

** This version had a build error

Fully removed django-contrib-comments dependency.

Removed the module from the list of requrements, and made
additional changes to get the tox tests passing.

* Resolve test issues on APICommentSerializer.
* Resolve flake8 errors on travis build