don't run image regression tests on travis
don't run image regression tests on travis

jpinedaf/pyspeckit,dinossimpson/pyspeckit,allisony/pyspeckit,keflavich/pyspeckit,jpinedaf/pyspeckit,keflavich/pyspeckit,vlas-sokolov/pyspeckit,pyspeckit/pyspeckit,dinossimpson/pyspeckit,e-koch/pyspeckit,mikelum/pyspeckit,low-sky/pyspeckit,pyspeckit/pyspeckit,bsipocz/pyspeckit,bsipocz/pyspeckit,keflavich/pyspeckit-obsolete,low-sky/pyspeckit,e-koch/pyspeckit,allisony/pyspeckit,vlas-sokolov/pyspeckit,mikelum/pyspeckit