We no longer need special overrides for Wheel dependencies
Merge pull request #254 from dstufft/remove-wheel-dependency-overrides

We no longer need special overrides for Wheel dependencies
Add support for user sessions
Add a basic framework to handle user authentication
Add the start of a template and CSS work for a login form
Implement CSRF
Move the classes to the top of warehouse.sessions
Remove note about nonlocal, we've switched to Python 3.4
Rework the session handling to use a dispatch_view decorator
Store our sessions inside of redis

* Use msgpack to serialize the sessions for more compact
  storage and for faster serialization/deserialization
* Move the session cycling support into our RedisSessionStore
* Expire our redis sessions after 12 hours, but renew the session
  on every interaction with Warehouse
Move our random token support into warehouse.utils
Use warehouse.utils.random_token for our CSRF tokens