Git commits in Moodle 2.6.x by Jody Steele

commit add50b5ab0c237c951e6392e0e447e394c91f4f8
Author: Jody Steele <steelej@queensu.ca>
Date:   Wed, 16 Oct 2013 23:19:34 +0800
Tag:    v2.6.0-rc1

MDL-38628 mod_assign: Allow a user to specify "No Grade" when grading an assignment submission