Change hardcoded value for a runtime value which can be overriden
Fixed Warden not being able to authenticate.

Issue was two folds: First, the manager was not set to use any
strategies, even if there was a strategy available. So this first part
fixes that.

The second issue was a way more subtle. I was using @controller.env
variable which isn't the same as @request.env. Because of that, I didn't
have a working Request object that I could get information from to
authenticate the user.
Fixed how the user's email is generated
Warden's manager doesn't actually work in a test.

So I need to fix this by making sure all supposed env have warden's
proxy.

Those kind of fix are ugly, but I have to understand better how tests
work. My process is probably wrong here and maybe I should do
integration tests instead of functionals one.
Added a route to login from
Changed strategy to fail with a message on every try

Previously, the message would only be passed under certain
circumstances. Since the message is meant for every scenario, it should
be shown in every scenario where the authentication fails
Added login screen with error handling
Added test coverage for login screen
Merge pull request #67 from pothibo/admin

Admin is now accessible via /admin