Move test requirements out of tests dir.

Transfer contents of tests/requirements.txt into more appropriately
named dev-requirements.txt in the project root.
Update dev-requirements.txt to include base requirements.txt.
Rename players.py.

Move tests/integration/players.py out of the integration dir into tests
as test_player_creation.py.
Use nose.

Update dev-requirements.txt to use nose. Make appropriate changes in
.travis.yml. Remove unnecessary Python versions in .travis.yml.
Use WebTest.
Update test_player_creation.py to use nose and WebTest.
Make player creation test check for valid response.
Update player creation test to verify POST status code.
Merge pull request #34 from reillysiemens/tests

Improve testing.