adding logic to determine if file is an image refs #722
adding logic to determine if file is an image refs #722

jeremyf/sufia,samvera/hyrax,samvera/hyrax,zhang4952/scholarsphere,samvera/hyrax,jeremyf/sufia,ndlib/scholarsphere,zhang4952/scholarsphere,zhang4952/scholarsphere,ndlib/scholarsphere,samvera/hyrax,zhang4952/scholarsphere,ndlib/scholarsphere