Adding the ability for the backend to support inactive users.

Django 1.5 does this as default, so we should support it.
Removing some rogue \n statements.
Updating check_account docstring.
Moving our API_KEY_ID / API_KEY_SECRET / APPLICATION_HREF.

We now have class variables with these values -- this way we don't need to
pollute our code with them (this simplifies things a bit).
Updating check_account docstring, removing legacy param docs.
Updating the StormpathBackend docstring.
Updating the check_account docstring, to be more explicit.
Renaming import for clarity.
Further simplifying the global variables for Stormpath API auth.
Making a new global, `application`.

This handles our client / application fetching on object creation, instead of
doing it during run-time.
Updating the `authenticate` docstring to be more explicit.
Cleaning up the `get_user` method definition.
Updating the `save_user` helper.

Simplifying the logic, rewriting the docstring.
Updating the save_user method.

It was improperly setting the user's dummy password previously, this commit
fixes the issue by setting a real dummy password using the User.set_password()
method Django provides.
Adding a note to our `save_user` helper.
Removing now redundant comment.
Fixing formatting.
Adding whitespace for style.
Simplifying get_full_name() implementation.
Adding whitespace for style.