Changed confederations from Collection to choice

 On branch master
 Your branch is up-to-date with 'origin/master'.

 Changes to be committed:
	modified:   README.md
	modified:   cobra/items/__init__.py
	modified:   cobra/items/competition.py
	modified:   cobra/items/confederation.py
	modified:   cobra/items/team.py
	modified:   cobra/items/user.py
	modified:   setup.py