activitycentra.com => unleashkids.org
update docs to clone 5.0 rather than master
in docs, clone a real branch rather than just a tag, because the HEAD moves automatically, in case we forget to move the tag when we add a fix
Merge pull request #128 from georgejhunt/release-5.0

Release 5.0 -- Change the INSTALL docs to clone the release-5.0 branch