Rename js/func.js to js/underscore.js
Change the way _ (underscore) object is extended with new functions.

Modules now load underscore through js/underscore.js instead of through
lib/underscore.js module. Underscore in lib is the actual underscore
library while the underscore in js folder is where custom functions are
added to underscore via _.mixin function.
Add d3.js wrapper.