MS-603: add picturefill to main.js in build
MS-603: rename images correctly
MS-603: implement retina selective targetting
MS-603: only use retina at width 1200px
Merge branch 'develop' of http://github.com/myplanetdigital/neompd into MS-603-image-size-detection
MS-603: add retina choice to post tile images
MS-603: consistent definition for img size
Merge branch 'MS-603-image-size-detection' into develop