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 :)
ah ok, I was looking at another project and I guess we have the route defined slightly differently. The following produces the situation I was talking about: 

```
resources :teatimes do 
  resources :attendances, only: [:show]
end
```