Require/ban the width descriptor based on presence of sizes. Fixes #114
Require the media attribute when using multiple sources. Fixes #115
Merge pull request #117 from zcorpan/fix-115

Require the media attribute when using multiple sources. Fixes #115
Added type to authoring conformance of multiple sources
Fix ul closure
Removed the MIME type restriction on the type attribute
Removed the valid mime type restriction
Merge pull request #120 from yoavweiss/gh-pages

Enable multiple sources without `media` when `type` is involved
Make invalid sizes skip to the next source, or ignore the srcset attribute for img. Fixes #113
Merge pull request #122 from zcorpan/fix-113

Make invalid sizes skip to the next source, or ignore the srcset attribu...
Merge pull request #116 from zcorpan/fix-114

Require/ban the width descriptor based on presence of sizes. Fixes #114
Add HTMLImageElement#sizes. Also tighten up the authoring requirements for the various attributes.
Allow the type attribute again
Remove extra 'it'
I was behind origin apparently, so merge...