ENYO-2676: Add enyo.dom.hasClass/addClass/removeClass methods, use them for setting classes on html and body to avoid duplicat after multiple renders.

Enyo-DCO-1.1-Signed-Off-By: Ben Combee (ben.combee@lge.com)
Merge pull request #366 from enyojs/ENYO-2676-unwiredben

ENYO-2676: Add enyo.dom.hasClass/addClass/removeClass methods, use them ...