add spectral-cube to travis
add spectral-cube to travis

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