IE8 Fixes (part 2)

Three small fixes here:

* #434 - CSS tweaks: Adding fallback colors for `rgba`, and swapping `::after` for `:after`
* #435 - Enable CORS support in jQuery
* #430 - Click event handler changes
It doesn't look like `crossDomain` does the trick.  Adding it causes the same error as before.

    opts =
      type: method,
      dataType: "json",
      error: this._onError,
      headers: this.options.headers,
      crossDomain: true

in [`store.coffee`](https://github.com/openannotation/annotator/blob/master/src/plugin/store.coffee#L211-L215).

I think this is forcing [jQuery to enable the feature](http://api.jquery.com/jQuery.support/) which is disabled otherwise?