Changes from Picturefill 2.3 Beta:

Spec Matching

• Invalid sizes values now fall back to 100vw default (f379528073d875089bc594900079b09184dd4f69)

Bugs

• Fixes a potential race condition when using type (3fba68de8b0df200e36b56dcfb01f89e09f8d4d0)
• Prevents a fatal error in IE8 when assigning an undefined width (d1f5a1fd550e30545f7b4c66b94e4838bab1a720)
• Prevent IE10/11 from setting an inherent width of zero on SVGs (742c66c0a93e7d417e58f1a50238371c3c1d6ef6)
• Fixes an error that prevented Picturefill from being handled as a named AMD module (a5859fb564fd32d4ca3643277ccb35025a93214a)