Allow targeting of * for required fields

Currently you can't target the 'required' fields with CSS to make the * red (which is a fairly standard web thingy).

This allows you to use a .asterix class so you can make them red. .asterix was taken from the required field class used in the shipping/payment forms.
Merge pull request #1690 from curtismchale/patch-1

Allow targeting of * for required fields