When repo is renamed, also rename/move all references to the new name

[grepsedawk]

It's only a few sed's and some documentation changes, but maybe it would be neat to have a workflow that, when a repo is renamed, it modifies all refs of the old name to the new name -- then creates a PR.

Trying to rationalize this idea, this is actually quite helpful, because sometimes I come up with an idea for a shard/gem (or since a lot of this can get ported to https://github.com/grepsedawk/horseshoe, project names)... but the "name" holds me up, because I know it's a good bit of energy to hit all the renames if I chose to change it later, before release.