Rudamentary Firefox support

Preferences does not work yet, timestamps and localisation is buggy,
and CSS is misaligned. But it is remotely useable on Firefox now.
Add template tag to the correct location
Change insert location for switch to reddit button

Google+ is behaving irrationally as usual and is constantly removing
children inside of it, so the switch to reddit button is often being
removed, making it impossible for users to switch back to reddit, we
will insert the button outside of it and float it into position instead.

fixes xlexi/alientube#65