Relax the activesupport dependency constraint

[pmackay]

Would it be possible to create a release for this that can work with activesupport higher than 5.1.0?

[roll]

Hi @pmackay, we're having problems with maintaining Ruby code at the moment dut to lack of Ruby programmers.

Is there any change that you're interested in joining the @frictionlessdata/ruby team? Or maybe you know someone who is interested.

Joining the team means zero pressure of doing anything. It gives the maitain-level rights for tableschema/datapackage-rb in case if you have some time to resolve some issue like this. At the moment, I'm working on the document for all our teams to simplify the contribution workflow understanding.

Also, cc here to @samstarling, @reidab and @georgiana-b as other active people on the issue tracker.