Front end improvements

* Better structure for CSS file for easier contributions (e.g. separates reset from the main file, adds sectioning)
* Minor cleanup in the above
* Floated users list so you can see more at once (closes #21)

It's all temporary solution though as I think we need to switch UI to floats/flexbox (if we don't care about 100% compat, which I don't think we do?) to have fewer problems with borked layout on mobile. I'm game to do it.