CLC-4259 - Added method for cross-origin messaging of parent window to link to new location
CLC-4259 - Updated 'Back to Gradebook' link to send parent window back to Gradebook
CLC-4259 - Added Canvas::CoursePolicy#can_export_grades? method
CLC-4259 - Added Canvas::CourseUsers#course_grades method to return CSV containing grades.
CLC-4259 - Added CanvasCourseGradeExportController#download_egrades_csv
CLC-4259 - Removed unnecessary spec helper includes in CanvasCourseAddUserController specs