Change example to use correct content type of image/jpeg
Change example to use correct content type of image/jpeg

Silly little change, but it tripped us up. Files with 'Content-Type':
'image/jpg' were giving us browser warning, since it should technically
be 'Content-Type': 'image/jpeg'.
http://en.wikipedia.org/wiki/MIME_type#Type_image

beni55/knox,Automattic/knox,beni55/knox,Automattic/knox