Student pending

not done yet... but I'm up for comments/criticism!

Basically, a student asks to join a group, and they're put on a list of pending students (or coaches), and then anyone in the group can decide whether or not to accept them. So far accepting them doesn't work, but declining does. Mwahahahahaaaaa.

I was thinking that this couldn't be merged until some sort of notification system was in place, but Tobz thinks this isn't necessary. 

Still to do:
* [ ] alert group members that someone is asking to join their group somehow
* [ ] accept people wanting to join the group
* [ ] track down the probably many haml errors that happened during my rebase from master
* [ ] all da tests..... (this will most likely be a crazy fail right now)
* [ ] other stuff? Can a gif be fit in anywhere maybe?