DOC: Update CHANGES with gh-1379

Author: effigies

CHANGES

@@ -4,6 +4,7 @@ Upcoming release 0.13
 * TST: reduce the size of docker images & use tags for images (https://github.com/nipy/nipype/pull/1564)
 * ENH: Implement missing inputs/outputs in FSL AvScale (https://github.com/nipy/nipype/pull/1563)
 * FIX: Fix symlink test in copyfile (https://github.com/nipy/nipype/pull/1570)
+* ENH: Specify motion parameter source in modelgen (https://github.com/nipy/nipype/pull/1379)
 
 
 Release 0.12.1 (August 3, 2016)