replaced np.ma.median with np.median in test_combiner_with_scaling
replaced np.ma.median with np.median in test_combiner_with_scaling

mwcraig/ccdproc,indiajoe/ccdproc,pulsestaysconstant/ccdproc,evertrol/ccdproc,crawfordsm/ccdproc,astropy/ccdproc