Add groups to model
Add groups to division details page
Add division-team-player association, remove team-player association
Merge branch 'master' into division-team-player-group-model

Conflicts:
	app/controllers/divisions_controller.rb
	app/models/division.rb
	db/schema.rb
	spec/models/team_spec.rb
Fix style
Merge pull request #12 from elisapp/division-team-player-group-model

Add division-team-player, group model