fixed loadCSS for ie9+ and other browsers
Merge branch 'master' of https://github.com/straker/AssetManager

* 'master' of https://github.com/straker/AssetManager:
  fixed example not calling requestAnimationFrame shim, updated README.md with IE9+ compatability
  Update README.md
  Update README.md
  Update README.md
  Update README.md
  Update README.md