Merge pull request #309 from nanan9177/feedback_collect

Added the capability of showing gathered hints to students.
Merge pull request #310 from nanan9177/feedback_collect

Recording activity whenever a student receives a hint.
Merge pull request #311 from nanan9177/feedback_collect

Fix the case when no activity was created.
flappy related string changes
Merge pull request #312 from code-dot-org/flappy

flappy related string changes
Don't allow students without email to end up without a teacher
Merge pull request #313 from code-dot-org/dont_allow_remove_student_without_email

Don't allow students without email to end up without a teacher
[Finishes 66739346]: Remove 2 bounce levels, modify seed.rake to delete script_levels missing in CSV
Merge pull request #314 from nanan9177/feedback_collect

Feedback collect
[Finishes 66739328]: Success criteria for level 7
Merge pull request #315 from code-dot-org/remove_bounce_levels

[Finishes 66739346]: Remove 2 bounce levels, modify seed.rake to delete script_levels missing in CSV
merge
Merge pull request #316 from code-dot-org/pivotal_66739328

[Finishes 66739328]: Success criteria for level 7
tweak add_to_home to hide browser ui, not pop up while embedded in facebook
Translations
add two new levels
Merge pull request #317 from nanan9177/feedback_collect

Adding the puzzle link to add hint page.
change to new levels
more string tuning
Merge pull request #318 from code-dot-org/flappyNewLevels

Flappy new levels