Gracefully handles "KeyboardInterrupt"

Catches "KeyboardInterrupt" during user input and calls ``sys.exit`` with a proper message to the user.
Merge branch 'master' of https://github.com/audreyr/cookiecutter

Conflicts:
	cookiecutter/prompt.py
Added BoilerplatePP to Cookiecutter list
Add a link to cookieforms.
Add @uranusjr to AUTHORS
Cleaner config prompt design inspired by bower and npm
Merge branch 'visually-cleaner-config-prompt' of https://github.com/robinandeer/cookiecutter into visually-cleaner-config-prompt