Implement new font picking UI

[xmatthewx]

To make things simpler for users, we should select a handful of fonts instead of offering all the fonts.

We might also fetch the characters in their name so we can show how they look in the menu itself. Like so: http://fonts.googleapis.com/css?family=Opens+Sans&text=OpenSans

A few from the league of moveable type on google fonts: Knewave Londrina Sketch Pacifico Open Sans Prociono

[toolness]

Here's the relevant screenshot from reference.html:

[toolness]

Done in b65a9af47131259449f81651c199af82425095c5.