Rework squares class to represent 'SERVING' state.

In addition, I made the GCE class pass more information down and more flexible about how heartbeats work.

Added FontAwesome (http://fortawesome.github.io/Font-Awesome/) so we can have scalable icons.  Use this for check boxes when instances are serving and for a cool new spinning icon when ajax request is outstanding.

Fix up gce.js and squares.js to declare instance variables in constructor instead of prototype.  Variables on the prototype are 'shared' variables.

Changed square colors to use official Google logo colors.