prove issues parsing srcset URL descriptors pairs
use the spec's algorithm to process image candidates

the old parser didn't conform to the spec:
http://www.whatwg.org/specs/web-apps/current-work/multipage/embedded-content-1.html#processing-the-image-candidates
this fixes #8
Merge pull request #10 from tim-evans/parsing-algorithm

Rewrote parsing algorithm to conform to the srcset spec
Add warning project won't reduce bandwidth use for mobile devices #11
Update grunt to 0.4.0.
Avoid javascript errors in IE8 (though still fails in IE8.)
Fix width and height detection for IE8.
Replace warning with friendly hints
Merge pull request #14 from douglascross/master

Making it work for IE8 + Upgrading Grunt
Merge pull request #12 from michrome/double-download-warning

Add warning project won't reduce bandwidth use for mobile devices #11