Student feedback

[LukasMac]

Finalised student feedback.

To send email requesting feedback use: rake feedback:request (for now you can only do this for the most recent session).

@todo left:

1. admin side for feedback review
2. not sure if it is done, but in case if it's not: we need populate content to Tutorials table
3. I wrote email template asking for student feedback, I think it needs review :)

P.S. Sorry for delay to finishing this out.

[coveralls]

Coverage remained the same when pulling fd43891 on LukasMac:student_feedback into 04eefaf on codebar:master.

[despo]

@LukasMac thank you. Great works 👍 😄
I will try and the tutorials table populated and the email review. I'll also add a separate task for the admin section.