Adding 'nice' process priority parameter to jobs

[paulgoodchild]

Firstly, absolutely love this Jobby system. Thanks for providing and maintaining this.

I've come up against an issue where we're running background processes, some of which are quite intensive in different ways.

A nice addition would be to add a nice process priority to each command that gets kicked off? So instead of just:

php cmd args etc.
you could have:

[nice [priority]] php cmd args etc

I can maybe have a dig around the code to see how straight forward it would be to add this and offer a PR? If I did so would you look to incorporate it?

Can you foresee any issues with this?

Thanks!