Element.transform().toString() fix attempt

Sometimes calling .transform().toString() returns an object, instead of a string.

elproto._.transform gets assigned to the toString() property of the transform() return value,
but this value is an object.

Sample case:
http://jsfiddle.net/bitblitter/hUWT7/3/
Merge pull request #253 from bitblitter/dev

Element.transform().toString() fix attempt