Attendance update route can now take a reason from params. Updates #78

Also not tested. All I could do in a few minutes before going to work. 

- Created a new Attendance controller and pointed update route to it
- Passed in `reason` param to `flake!` method as part of opts and assigned it
to the record. 

This could use a unit test for `flake` and a feature spec as well. I'll see if I can
do it tonight :)
[DYES, bro?](http://www.starwarsautographcollecting.com/Autographs/Spaceballs/Yogurt.jpg)

(All the tests are *Spaceballs* references)