Run django==1.5.4 on travis
Fix json decoding error on python3 and added test case changes to support .json() method on _request

Problem fixed:

'response.content' is returned as a byte array, and json.loads will choke on it, leading to a failed log-in attempt, which you'd have see in the django logs as:

Failed to parse remote verifier response: `b'{"audience":"[redacted]","expires":1387148033218,"issuer":"gmail.login.persona.org","email":"[redacted]","status":"okay"}'`
Fix #222 - BROWSERID_AUDIENCES not necessary in debug mode
Add .persona-button to login button by default (if none provided).
Doh, forgot to update AUTHORS.
Note to self, check test method names more carefully.
Fix #196: Add support for BrowserID in the admin interface.

Also changes browserid_login and browserid_logout to not auto-add the
browserid-login/browserid-logout classes to links that they generate,
in order to allow code to use the helpers without forcing the buttons
to use the login code from browserid.js (the admin utilizes this).

Also also adds some licensing comments that we were missing.