CurdlingLocator._get_project() should return None on failures
Use urllib3 to PUT files on curdling servers. Closes #6

With that change, we're just removing `requests` from our
requirements.txt file.
Fix functional tests and simplify get_locator()
Increase test coverage, we're 73% now

A couple small tests were written to improve the stability of the main
features provided by curdling. This commit re-introduces the commented
check for packages installed. It also adds a bunch of new tests,
improvements and fixes to others.