Merge branch 'mel-wrap' into 'master'

BUG: remove melodic wrapper assertion that input is nifti

Closes #377

See merge request fsl/fslpy!321

fsl/wrappers/melodic.py

@@ -50,8 +50,6 @@ def melodic(input, **kwargs):
         'logPower'     : wutils.SHOW_IF_TRUE,
     }
 
-    asrt.assertIsNifti(input)
-
     cmd  = ['melodic', '--in={}'.format(input)]
     cmd += wutils.applyArgStyle('--=', valmap=valmap, **kwargs)