DOC: point to image generation script

in comment in RST file.  Add more specifics of needed images in script
comments.

Author: matthew-brett

doc/source/coordinate_systems.rst

@@ -141,6 +141,8 @@ has a red box that shows the position of the slice block for
 ``someones_epi.nii.gz`` and a blue box for the slice block of
 ``someones_anatomy.nii.gz``:
 
+.. images generated by <nibabel>/doc/source/scripts/make_coord_examples.py
+
 .. _localizer-image:
 
 .. image:: /images/localizer.png

doc/source/scripts/make_coord_examples.py

@@ -1,9 +1,13 @@
 #!/usr/bin/env python
 """ Make graphics and example image for coordinate tutorial
 
-Expects MNI nonlinear template t1 and t2 images in directory of script.
+Expects MNI nonlinear template t1 and t2 images in directory of script -
+specifically these files:
 
-Requires nipy and matplotlib
+* mni_icbm152_t1_tal_nlin_asym_09a.nii
+* mni_icbm152_t2_tal_nlin_asym_09a.nii
+
+Requires nipy and matplotlib.
 
 Executing this script generates the following files in the current directory: