Update Tagging doku and commands

[rwaffen]

We have this too in other places, but I feel it's broken for a bit of a nit pick reason.

If you have a merge commit then the history is very confusing because you end up tagging the merge commit, not the commit named "Release $version". Because of that I'm more a fan of a fast forward merge and tag that.

For Foreman releases I use https://github.com/theforeman/foreman-installer-modulesync/blob/master/bin/release-merge which calls https://github.com/theforeman/foreman-installer-modulesync/blob/master/bin/release-module to actually release. Note we don't have release actions to run after a push, so for Vox Pupuli it could be simplified.

This works well together with https://github.com/theforeman/foreman-installer-modulesync/blob/master/bin/release-pr to create the actual PR.

Originally posted by @ekohl in voxpupuli/container-puppetserver#115 (comment)