Update README.md

Please update readme.md in this section:

cd redmine
git remote add upstream -m master git://github.com/openshift/openshift-redmine-quickstart.git
git pull -s recursive -X theirs upstream master

Please insert 1 more command
after "cd redmine"
"git init"

Because without it you'll get - "fatal: Not a git repository (or any of the parent directories): .git"
after this command "git remote add upstream -m master git://github.com/openshift/openshift-redmine-quickstart.git"