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
Sorry, I've just looked at this again, and this is absolutely not what we want to be doing. `jQuery.support` is intended to be a *read-only* feature detection object. Altering the values of properties on this object doesn't make sense. Ref: https://api.jquery.com/jquery.support/