Allow specifying additional arguments to on-demand tasks (Resolves #74) and related changes:

1) Run now buttons for on-demand requests now open a vex prompt instead of a confirm
2) Optional argument data is passed to jQuery Ajax data (with processData false)
3) Individual request page now has a refresh method and will refresh itself 3 seconds after the response from `/run` is finished (in my testing, this was enough time for the new active task to show up)
4) Run now button on individual request page now actually works :P lol