Class attribute classes should not be prefixed

[jacojoubert]

If a class is assigned using the class attribute like so {{ui-component class="custom-class-name"}} it should be outputted as is and not get turned into this ui-component--custom-class-name.

[ebryn]

This is a known issue with our template rewriter: #53

[ianstarz]

@ebryn @jacojoubert do we want to continue to whitelist/add exceptions to the rewriter? What is the reasoning behind this exception?

[ebryn]

Closing in favor of #53, let's discuss there if necessary