Delete username/password from session on logout

Then we can know that logged out sessions will have a nil username/password.
Merge pull request #20 from clehner/fix-empty-username2

Delete username/password from session on logout
Increases font size
Silences stupid could not get latest post warning
Allows ordering by last visit on admin panel
Moving mark all as read to bottom
Adding screenshot to README
Make the first user to sign up be admin.

Fix #15
Adding demo link.
Merge pull request #22 from clehner/initial-admin

Adminify the first user.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	templates/static/style.css