Make larger area clickable to trigger computation

Until now, one had to aim for the metric meter or the text inside in
order to trigger a computation. Now quite a large area is clickable to
start a metric computation. Also I added the submit button again to
select the current repository.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add sidekiq web frontend

Sidekiq also offers a nice web frontend to visualize and manage the
workers. I have added the required gems and set the mount route.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>