`srcset` parsing test, currently failing.
`srcset` parsing tests for days, some of which currently fail.
Require lossless and alpha support for WebP

Testing for lossless WebP should help to avoid false positives when a
browser does not support lossless or alpha WebP.
Merge pull request #212 from kristerkari/fix-webp-test

Require lossless and alpha support for WebP
Added @kristerkari to authors
Reverting advanced `srcset` syntax unit tests.
Closes #213 - Removes `100%` syntax in favor of `100vw` in examples, shims `vw`.
Comment no longer applies.
Don’t dodge the existing `srcset` if it’s natively supported.
Update dist files.
Reduced number of calculations on resize event
Reverts change in ef17c0456c441a812311664207727de32f7b8d66, fixes #216
Reverts demo page back to normal.
Updating docs page with new download heading/links.
Add space between a and srcset
Fix indenting for getWidthFromLength
Merge pull request #220 from nschonni/patch-1

Fix indenting for getWidthFromLength
Closes #223 - Omitted  with  in play now fails silently; test to back it up.
Sturdier test for #223
Fixes refression in 4c3cceab4d97ac7176ae58ae5c2f54e3babb7609 where browsers with native `srcset` support that had `sizes` polyfilled weren’t showing anything.