Refactored mass_update to improve response time, moved caching scores to a background worker and refactored mass_edit to use eager loading (fixed 1+N problem that was hidden in the edit view) and significally improved response time
Added a Hash helper method to find a nested key values
Switched student_id to student
Lazy created grades for no grades students and auditors
Refactored remaining grading methods and integrated the grade update worker
Fixed undefined method pluck for Array
Merge pull request #826 from UM-USElab/grades_worker

Grades worker