Updated to Rufus-Scheduler 3.0 syntax

[xander-miller]

• modified gemspec to require rufus-scheduler >= 3.0.0
• modified scheduler call to use .new instead of previous .start_new syntax

[davefp]

Oops! I just merged a fix to restrict the gem to version 2.x.x. Bad timing on my part. Please rebase this PR so that it merges cleanly and I'll get it in.

[xander-miller]

K, I fixed it. I think, first time trying to update a fork to an upstream master.

[gordhawkins]

Doesn't work for me. As soon as I try to switch to 3.0.2 the jobs stop pushing data to the dashboard. Switching back to 2.0.24 solves the problem. Any thoughts?

[terraboops]

As @gordhawkins has pointed out, this change seems to be a breaking change and as such should wait for the next major release to be merged.

The migration path is pretty clear though, simply replace .start_new with .new in all jobs. Perhaps the change is small enough to be merged? Thoughts?

[monfresh]

Hi. Just checking on the status of upgrading to rufus-scheduler 3.0? I'm not sure I follow the issue with start_new. It looks like Dashing has been using .new for a long time now. Is rufus-scheduler 3.0 still causing breaking changes?