Release v0.3.3

[alecglen]

nfl_data_py 0.3.3 fixes the test suite and resolves all submitted issues that were easy to fix while still supporting all the way back to Python 3.6 and associated dependencies. This is intended to be the final, stable v0 release before the impending upgrade to nfl_data_py 1.0.0, though bug and security patches may still be submitted in the future.