Test token mismatch
Sets back session key to rack.session

Since this didn't fix the CSRF protection bug for new users
Bumps rack-protection to v1.5.1

Fixes bug where new users would not have session key, thus getting a
CSRF exception.

Explanation:
https://github.com/rkh/rack-protection/commit/c415d50c7ce97d35c8fae706dbed3390330b983d
Merge pull request #20 from wilhelmbot/csrf-fix

Csrf fix