Added support for player season stats.
Update player_season_stats.rb

Fixed a typo in the spec
Refactored the team_roster to use the generic player class.
Merge branch 'master' of github.com:rottmanj/sports_data_api
Refactor & added support for player season stats

Pull request #24

Merge branch 'master' of https://github.com/rottmanj/sports_data_api into rottmanj-master

Conflicts:
	lib/sports_data_api/nfl.rb
	spec/cassettes/sports_data_api_nfl.yml