Add middleware for canvas apps:
add memcache to development requirements, otherwise tests fail with ImportError: No module named memcache
add middleware for canvas
if referer not facebook, we pass
add error denied detection
redirect user when app not authorized
connecting user when permissions are given
add verification for same user
checking for permisions
changed behavior for error in order to reauthenticate
made pep8 complaint
Merge pull request #256 from duduklein/facebook-canvas

Add middleware for canvas apps: