Support parsing class names instead of loading CSS via XHR

[Mr0grog]

Right now, we have to load the CSS via XHR because the parsed stylesheet info doesn't contain unrecognizable selectors (which would include any selectors with :media() in them).

If we could parse the class names we replace media queries with (e.g. query_min-available-width_200px), we could do everything without needing to reload via XHR. Not as nice for an author, though. Maybe a useful optimization when using a build tool?

Probably not worthwhile unless someone really wants to use this in production as more than a proof-of-concept.