Nfl-data-py

- Added import functionality for participation, contract, and player data made previously available through nflReadR

- Actually fixed issue between python and pandas not resolved in 0.2.9
- Dropped python 3.5 support from nfl_data_py to allow for parquet file usage

- Fixed compatibility issue between python and pandas

Changed
- Redirected data pulls to new repos

Changed
- Updated cache feature to be OS agnostic

Changed
- Fixed bug in cache process that was effecting pbp load too