Styling on /users to float, auto complete usernames in chat

This is just a start on giving you a list of usernames to reply to when typing in chat.

To test:

Load up chat, start typing a name of someone in chat, a list will appear, click one of the usernames with your mouse.

Later, I will refactor to give more keyboard support. 

closes https://github.com/bigboringsystem/bigboringsystem/issues/21
closes https://github.com/bigboringsystem/bigboringsystem/issues/4