[ FLOC-1010] Improvements to the release process documentation

Fixes https://clusterhq.atlassian.net/browse/FLOC-1010
I don't like this. It means that any warning like "If you have version 1.2 or below, do this uninstall step first" may be wrongly changed. Hopefully that would be spotted by a reviewer but a much better way to do this is to have keywords substituted (like `|version|` is elsewhere) in the relevant places.