unit conversion fix: there was a major bug in which convert_to_unit had no effect at all
unit conversion fix: there was a major bug in which convert_to_unit had
no effect at all

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