heroku times out for long-running requests from the dashboard

[deargle]

Certain large batch requests from the dashboard, such as the big "approve all" button on the Hits tab, take too long for heroku, and will timeout. However, scheduling an approve_all task will not time out. This is because heroku has a cap on how long a browser request can be open before it cuts it off. On the other hand, a scheduled task requires to browser connection. One solution, then, is to have those buttons on the dashboard submit one-time tasks. A downside of this is that it would require do_scheduler to be running. OTOH, it's not a good idea to have long-running requests open on heroku anyway if participants could be taking the study at the same time.

Kind of rambling, but thought it would be good to jot down.