Fix content nil issue in gradings
Fix error caused by access of un-enrolled user trying to attempt a assessment.
Merge branch 'development' of https://github.com/Coursemology/coursemology.org into undefined_method_levels
Merge pull request #180 from wangqiang1208/bugfixing/course_96_grading

Fix content nil issue in gradings
Add back permission check.
Merge branch 'development' of https://github.com/Coursemology/coursemology.org into undefined_method_levels
Question number starts from 1 instead of 0.
Increase line limit, show cop names
Merge pull request #183 from jsyeo/jsyeo-line-cop

Increase line limit, show cop names
Merge pull request #182 from DIdiHL/fix_auto_graded_question_index

Question number starts from 1 instead of 0.
fix potential nil level
Merge branch 'development' of github.com:Coursemology/coursemology.org into development
Simpler enrollment checking.
Use rubocop v0.22.0 style declaration
Merge pull request #186 from jsyeo/jsyeo-line-cop

Use rubocop v0.22.0 style declaration
Merge pull request #181 from DIdiHL/undefined_method_levels

Undefined method levels
Fix answer grading nil bug in grading controller action new
Merge pull request #189 from wangqiang1208/bugfixing/assessment-gradings

Fix answer grading nil bug in grading controller action new