STYLE: Autogenerated files ignored

Two files that are auto-generated with slightly different results on
every run (due to randomness???) should not be part of git.

Author: hjmjohnson

.gitignore

@@ -14,4 +14,6 @@
 .pydevproject
 .idea/
 /documentation.zip
-.DS_Store
+.DS_Store
+nipype/testing/data/von-ray_errmap.nii.gz
+nipype/testing/data/von_errmap.nii.gz