use requests and requests-oauthlib to simplify code and make it Python 3 compatible
bumped version to 0.2.0, updated setup.py and requirements.txt
added test for Board.get_cards and Card.delete -> 0.2.1
Extended test for Board.get_cards
rename to changelog
update changelog(s) for 0.1.6
bump version
Merge branch 'master' of https://github.com/gameloop/py-trello into gameloop-master

Conflicts:
	setup.py
	trello/__init__.py
Merge branch 'gameloop-master'