Email improvements

[bmyerz]

do this all on localhost only

• when running on flask server localhost email button should behave in a way simulates the expected behavior. When you click it, it should turn to the sending icon and after a delay of 10seconds it should say Emails Sent.
• fix: first time you go to the page it already says Emails Are Sent!
• fix: after clicking Email button, it seems to hang on "Sending..." forever
• on localhost instead of sending actual emails, generate them and save them as files.

second steps

• Test emails on dev server to ensure working properly

Lower priority

• add button next to Email that says Download student feedback forms (so instructor can distribute them another way or simply look at a sample feedback form)
• Test: Do emails get sent to all teams or only those who have been rated for this evaluation?
• progress bar instead of spinning

[bmyerz]

closing #146 in favor of this one

[bmyerz]

tracking this issue in PR #201