Please review: new wiki page with release instructions

In order to allow other people than me to make releases in the future, I tried to write down a step-by-step guide to making a release (the page is linked from the wiki homepage): https://github.com/haskell/cabal/wiki/Making-a-release I'd appreciate if people could take a look and see if there's something missing (e.g. the actual build steps using a sandbox tend to not always work, asking me to re-configure as the Cabal version changed.)