ensured that videoFactory respected the `stretchImages` config option
ensured that videoFactory respected the `stretchImages` config option

changed the video poster image to use `imageFactory` so that it would
respect the `stretchImages` configuration option

prosanelli/blueimp-gallery,weddingwire/blueimp-gallery,prosanelli/blueimp-gallery,weddingwire/blueimp-gallery