Add pagination to jobs list

Hi,

I've added a paginator to the job listing, showing one hundred items per page, as this is the [Django's default](https://github.com/django/django/blob/1.6.5/django/contrib/admin/options.py#L377).

Seems there is some sort of confusion regarding the `0.7.0` tag and the `master` branch, as stated on #67, but looks like there is no other branch to pull. Anyway, I can send this again if you like.

Regards,
Tiago.
`queue.jobs` will fetch all the jobs from Redis and can potentially be a very expensive operation. We should use `queue.count` instead :)