Git commits in Moodle 2.8.8 by Clement Smith

commit 454882a4fa3e0000a4ed0b2edc7361242481aa25
Author: Clement Smith <cdsmith@umn.edu>
Date:   Thu, 30 Jul 2015 22:00:26 +0800
Tag:    v2.8.8

MDL-50963 lang/en/grades.php: Improve bad grade error message

commit 3c23486ad2b5dac4ff4362d8349847f09abfd68e
Author: Clement Smith <cdsmith@umn.edu>
Date:   Thu, 30 Jul 2015 20:44:42 +0800
Tag:    v2.8.8

MDL-50957 grade/report/user: Fix division by zero