A few more variables in the css files, easier to customize

Pulled from work at mconf-ufrgs/mconf-web@master
Improve redirects after login

Solution based on:
https://github.com/plataformatec/devise/wiki/How-To:-Redirect-back-to-current-page-after-sign-in,-sign-out,-sign-up,-update

refs #867
Redirect back properly after signing in via shibboleth

It stores the latest "valid" page before a login via shibboleth and returns
to if after the login.

refs #862
Merge remote-tracking branch 'origin/branch-v2' into branch-v2-867-redicts-after-login
Add more tests to redirections after sign in

refs #867
Merge pull request #29 from mconf/branch-v2-867-redicts-after-login

refs #867