feat: Support for prerelease identifiers

As of semver 4.1.0 there is now support for setting a prerelease identifier.  https://github.com/npm/node-semver/issues/88

This PR adds support for passing the `preid` to semver increment. 
I named this to match the command line argument in node-semver

https://github.com/bromanko/node-semver/commit/56258fa42d007b19b671495403026f28a94455c2#diff-a342e6cbc646e03dc5b605ab42f5f28aR51

If you'd prefer something different I would suggest `prereleaseId`