Ref. #266 - Sets an inherent width to match native  behavior.
Serious code cleanup.
A couple of quick and sketchy tests for setInherentSize.
setInherentWidth now polls to make sure the image in question is ready before attempting to set a width.
Merge branch 'inherent-width'

Conflicts:
	dist/picturefill.js
	dist/picturefill.min.js