Add fallback for IE 8 and older

The <a
href="https://github.com/MoonScript/jQuery-ajaxTransport-XDomainRequest"
 target="_blank">XDomainRequest</a> plugin should work for IE8 also and
I think it did work, but it was choking on D3, maybe need to try <a
href="https://github.com/jquery/sizzle" target="_blank">Sizzle</a>
Only load XDomainRequest plugin for IE 9

...even though it's only 2k... not sure if that's efficient or not.
Also changed URL to use the CDN
Create README
Move Modernizr to load in body with other scripts
Move CSS and JS to their own files
Add some notes on dependencies to README
Remove `$.support.cors` for IE 9 support

It's the XDomainRequest plugin that fixed it, not this