Feature/picturefill

Updating to latest Largo core, stripping out CF-related picturefill code, and incorporating picturefill.wp plugin as an include into Largo itself (via inc/images.php). 

See demo at http://largo.bbyrne.cshp.co/trying-to-conceive-paypal-co-founder-max-levchin-has-an-app-for-you/

WP image sizes may want adjusting, and/or this plugin may want to be altered to accomodate non-standard image sizes if we want, but the core functionality should be solid.