WIP allow users to log in via Twitter
add dummy twitter secret setting for tests
add python-social-auth to requirements
use custom user model to store the user avatar
fix migrations broken because of the custom user model
fix test to check result form availability
add sign in with twitter icon
make the public Twitter key configurable with envdir
add new envdir settings to the README
Merge remote-tracking branch 'origin/twitter-auth'

Conflicts:
	README.rst
	templates/base.html