Merge pull request scottjehl#639 from scottjehl/3.0.2

3.0.2

Merge remote-tracking branch 'origin/master'

add additional mime types for apng

First release candidate for picturefill 3.0

Closes scottjehl#308 - Picture element examples are art-direct-y now.

Picturefill 3.0.0-alpha1

Picturefill 2.3.1

Picturefill 2.2.1 stable.

build