Adds modal overlay when exercise is completed.
Adds modal popup on completion of exercise streak.
Uses sprintf for modal generation. Fixes linting.
Fixes #2442
Merge pull request #2513 from anuragkanungo/css

Fixes #2442
Merge pull request #2499 from rtibbles/exercise_popup

Adds popup alert for exercise streak and overall completion.
remove unused set_exam_mode_off import
dump the values of the dict!
update with a correct playlist this time!