FIX: mark .niml.dset as special extension in filemanip

Author: mvdoc

nipype/utils/filemanip.py

@@ -74,7 +74,7 @@ def split_filename(fname):
 
     """
 
-    special_extensions = [".nii.gz", ".tar.gz"]
+    special_extensions = [".nii.gz", ".tar.gz", ".niml.dset"]
 
     pth = op.dirname(fname)
     fname = op.basename(fname)