Allow ID_LIST argument to run on comma-delimited set of IDs

Can now scripterate over a list of IDs, TO THE EXTREME!

```
$ ID_LIST=1,2,99,100 bundle exec my_script.rb
```

Also add a bit of helpful init text to show the redis list names:

```
Checked IDs being stored in redis list: one_timer_script:do_all_the_things:checked
Failed IDs being stored in redis list: one_timer_script:do_all_the_things:failed
Starting at 2014-03-19 15:14:46 -0700...
2014-03-19 15:14:46 -0700: Checked 0 rows, 0 migrated.
done
Finished at 2014-03-19 15:14:46 -0700...
```