Various (future) performance enhancements

Adapt Filament Group's enhance.js project for the base JS. Now all
CSS/JS is loaded ASYNC, with critical CSS inlined
Remove Modernizr.load, which is now deprecated; bump Modernizr to 2.8.3
from 2.7.1
Concatenate libraries into enhanced js
Add CSS for "enhanced" body class
Add Grunt support for grunt-critical-css task
Include critical css inline on production (In development, I just load
everything to make life easier)
Rename Grunticon output files to match the eventual cookie-based flags
I will use to load them (svg|png|fallback)
Moved icon loader out of the head and into oslc.js.
Added <noscript> fallbacks for both the base CSS and fallback icons
Build with all of the above

Related to issue #14