Add unit tests for sentry code

Signed-off-by: Tim Van Steenburgh <tvansteenburgh@gmail.com>
Run sentry server with python2

- Rationale: python-cherrypy3 is available in the archives for both
  precise and trusty, whereas python3-cherrypy3 is not, and we want
  to be able to install everything from the archives.

- Updated Makefile to run sentry tests with both py3 and py2

Signed-off-by: Tim Van Steenburgh <tvansteenburgh@gmail.com>
Revert new venv for local py2 testing

Let Travis CI handle the py2 testing instead.

Signed-off-by: Tim Van Steenburgh <tvansteenburgh@gmail.com>
Merge pull request #31 from tvansteenburgh/python2-sentries

Run sentry api server on python2