Fix search repo input styles

* Border box was not getting applied in firefox
Fix fonts on 500 page
Disable dot position rule
Error when Hound cannot be added

https://trello.com/c/AwlJCw48/191-there-are-cases-when-hound-user-cannot-be-added-because-of-permissions
Restore footer
Add more configuration examples

Also, refine wording to highlight that configuration is optional