Remove the mandatory use of ruby 1.9.3.

ruby 2.0 FTW.

Signed-off-by: François de Metz <francois@stormz.me>
Cleanup in user_session.

Signed-off-by: François de Metz <francois@stormz.me>
Extract methods to authenticator method.

Signed-off-by: François de Metz <francois@stormz.me>
Add session storage.

Signed-off-by: François de Metz <francois@stormz.me>
Fix callback login_successful.

Signed-off-by: François de Metz <francois@stormz.me>