Setup for releases with Minilla

One motivation for this is to prevent duplicate definitions of dependencies.  Minilla's `Build.PL` pulls them in from `cpanfile`.  We could do the same thing without "switching" to Minilla.  Minilla also regenerates other files, i.e. `README.md` and `META.json`, from existing content.  Minilla can also be used to bump versions and upload to CPAN for releases.  We just switched to using Minilla for UR as well.