Add task to clear sidekiq
Add task to clear sidekiq

I keep wanting to do this and end up in a console session copy/pasting
from the API docs:

```
https://github.com/mperham/sidekiq/wiki/API
```

This is better because now I don't have to remember anything.

artsy/bearden,artsy/bearden,artsy/bearden,artsy/bearden