Please use mozilla.dev.version-control going forward

[mc...@mozilla.com]

Since this is not a standard Mozilla list, i.e. not available on lists.mozilla.org, let's move future discussions to mozilla.dev.version-control. There have already been MozReview-related posts over there, so we can consolidate them into a single place. I've already updated the docs appropriately (http://mozilla-version-control-tools.readthedocs.io/en/latest/mozreview-user.html#getting-in-touch and http://mozilla-version-control-tools.readthedocs.io/en/latest/hacking-mozreview.html#discussion).

Thanks,
Mark