README.releasing.md

Steps to do on releasing

1. Run git flow release start <version>
2. change version number in App/perlbrew.pm
3. update "Changes" file
4. Run ./dev-bin/build.sh to build new standalone perlbrew executable
5. Run shipit -n to make sure no test failures. Fix test failures if any.
6. Run git flow release finish <version>
7. Run git checkout master
8. Run git push; git push --tags
9. Run shipit
10. Update webpages of release note etc