View all schedules for a job

Add a view to resque-web to list all the timestamps for which a given
job is scheduled.

![bar-jobs](https://f.cloud.github.com/assets/307121/1474170/fbc724c8-4629-11e3-8056-f33d563717bc.png)
![foo-jobs](https://f.cloud.github.com/assets/307121/1474171/ff7bcc40-4629-11e3-89d6-fb4dd49a0b5e.png)

Note: this work started from the discussion of https://github.com/resque/resque-scheduler/pull/167 with @meatballhat