git clone [email protected]:YOUR-USERNAME/YOUR-FORKED-REPO.git
cd into/cloned/fork-repo
git remote add upstream git://github.com/ORIGINAL-DEV-USERNAME/REPO-YOU-FORKED-FROM.git
git fetch upstream
git pull upstream master
git merge upstream/master
https://stackoverflow.com/questions/7244321/how-do-i-update-a-github-forked-repository/7244456#7244456