Implement CompatHelper to monitor dependent packages

[imciner2]

It would be useful to add the Julia CompatHelper (https://github.com/JuliaRegistries/CompatHelper.jl) workflow to this package to monitor the dependent packages and help with updating the compat entries. This bot will automatically run periodically and see if any new versions that no longer meet the compat restrictions are released, and then propose a pull request with the updated compat bounds. That PR should then run the test suite, and you can decide to merge it and get the compatibility entry. I think this would be a nice thing to have so that the compat entries don't get too stale, since very restrictive/old ones can begin to cause large problems (e.g. #118 was filed because this package was pining a DataStructures to an old version that then led to the diffeq stack being old, and plots being old, and the newer version of DataStructures was released in August).

[migarstka]

Thanks @imciner2
That is a good suggestion. I will set it up.