Adopt gem-release instead of Jeweler for releases

[pboling]

I was a HUGE fan of Jeweler.

But it is well and gone now. There was a fork, called juwelier, but it has an invalid copyright notice and license issues which get flagged by automated license checkers, so I would recommend against using it. I have been trying for several years to assist with fixing the issues with juwelier, but it iseems it has also fallen into disrepair.

I've been using svenfuchs' gem-release for a few years, and it has served me very well.

However, there are now built-in tools that can serve the purpose of releasing, and bumping the version manually isn't that hard.