Tests and coveralls integration.

This adds Coveralls integration. Be sure to set up a @harvard-lil account at https://coveralls.io/ . Then our Travis tests will automatically send test coverage info to Coveralls, which in turn shows up in a badge in our Readme. (Right now we're at 48%.)

This also refactors the tests into multiple files, and brings coverage for views/user_management.py up to 70%.