Rewritten login system. Both session and permanent. Pending tests writte...

Login system now using both session and permanent. User can choose which method.
When logging in users, email search is now done ``downcase``
You can only log out if you are already logged in
Logged in users are redirected to root URL if trying to reach Users#create or Users#new
Test for ``SessionHelper`` created.
Test for ``ApplicationHelper`` updated.
All pending tests are now implemented and is passing!

Fixes #37
Fixes #32