update the add method of enyo.Collection and its unit test for destroyAll

Enyo-DCO-1.1-Signed-off-by: Cole Davis <cole.davis@lge.com>
Merge pull request #489 from enyojs/collection-update

MERGE https://github.com/enyojs/enyo/pull/486 FIRST

Reviewed-By: Ben Combee (ben.combee@lge.com)