Test coverage

[fmontei]

This commit adds the initial unit testing framework for Deckhand. Included in this commit:

• tox job for py27 and py35 unit tests
• necessary testing requirements in test-requirements.txt
• a few unit tests for core api framework

Future tests will be written once the framework becomes more fleshed out.

[mark-burnett]

@fmontei I'm happy to merge this once it's out of conflict.

[fmontei]

@mark-burnett Thanks. This has already been merged in another PR. Going to abandon this.