Adding in the first pass of an App.Net Mixin for authentication and requests to their API.

I've taken the Facebook Graph Mixin as the example and have modified it to point to the right urls.

Testing comes next.
Adding in a demo app for App.Net.  I'm using the Facebook example as well since I started with the Facebook Graph Mixin.
Make sure we specify the response type in the extra params.
Specify the grant type when asking for the access token.
Adding in logging to confirm state that we're loading up the stream.
Transition from using the method off the parent class to build the url to actually building a request object.

We do this so we can specify the correct method (in this case POST) and the set the body correctly.
Convert the response correctly in the callback (json to pythonic) and request the user data with correct url.
Fix a typo with the base url.