Minor CSS and layout changes

I'm really impressed with the site! I spent a couple of months in western Uganda and had never seen much info on the local [Rutooro language](http://wals.info/languoid/lect/wals_code_rru) until I stumbled on your site today.

The Sources section on that page has a Google Book cover which extends outside its panel. I recommend a ```<div style="clear:both;"></div>``` at the end of the panel to keep it inside.

I also added some CSS which should make the homepage and language pages easier to browse on mobile.

I had minor suggestions for the maps, but the current JS is not in the repo.