rewrite upgrading
rewrite upgrading
rewrite first para to refer to specific release tags

It's true it's on master, but unwise to use that in production.
Also, it's helpful to link to the releases on github!
Merge remote-tracking branch 'origin/gh-pages-upgrading' into gh-pages-upgrading

Conflicts:
	docs/running/upgrading.md
Merge remote-tracking branch 'origin/gh-pages' into gh-pages-upgrading
explicit use of 'tag' now when referring to releases
Merge branch 'gh-pages-upgrading' into gh-pages