Updates all (classList, es5-shim, PIE) submodules
Updated getComputedStyle polyfill

From here (updated location for old one):
https://github.com/jonathantneal/polyfill/blob/master/source/window.prototype.getComputedStyle.js
Only load getComputedStyle polyfill when needed

Polyfill is only activated when a native one isn't already available.
Merge pull request #15 from usmonster/master

Updates getComputedStyle polyfill and all submodules