Merge remote-tracking branch 'brett/itsdangerous'
* brett/itsdangerous:
Call is_updated instead of testing it boolean.
Harden It's Dangerous key management.
First tests for the Session class.
Set a starting value for session.send_new_cookie.
Remove beaker stuff from the code.
Delete the session cookie on an empty session.
Back sessions with It's Dangerous.
Improve fs security for itsdangerous secret.
Docs for get_timed_signer_url.
Basic itsdangerous infrastructure.
Conflicts:
mediagoblin/tests/test_cache.py