added IE8 support

IE8 does not support getElementsByClassName. Whereever this is used and
not available I added querySelectorAll for browsers who support this
like IE8. You will still need a polyfill for Array.map like es5-shim in
IE8 though (https://github.com/es-shims/es5-shim)
added es5-shim to demo

Added es5-shim.min.js to the demo in /public to demonstrate that the
chosen order plugin works in IE8
Merge branch 'master' of https://github.com/rhafner/chosen-order into pr-rhafner
Rework @rhafner pull-request

Use only "querySelectorAll" instead of "getElementsByClassName"
Use a CDN for es5-shim
Update README.md with IE8 support info
Re-generate the scripts with Grunt