Fixed challenge_grades_controller
Fixed challenge_grades_controller

challenge_grades_controller now unfilters index so students may see the index and show views.

peterkshultz/gradecraft-development,mkoon/gradecraft-development,UM-USElab/gradecraft-development,mkoon/gradecraft-development,UM-USElab/gradecraft-development,peterkshultz/gradecraft-development,zqian/gradecraft-development,mkoon/gradecraft-development,zqian/gradecraft-development,zqian/gradecraft-development,peterkshultz/gradecraft-development,UM-USElab/gradecraft-development,UM-USElab/gradecraft-development