fix new grading email notification
Merge branch 'development' of github.com:Coursemology/coursemology.org into Deploy
remove used methods in mail job
refactor background job
refactor announcement
mail job refactoring
refactoring comments notification
fix rendering coding evaluation result for mission
fix uninitalized constant when creating comment
fix annotation email notification
Merge branch 'development' of github.com:Coursemology/coursemology.org into Deploy