update release checklist and .gitignore

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)

.gitignore

@@ -26,3 +26,4 @@ Vagrantfile
 docs/AWS_S3_BUCKET
 docs/GIT_BRANCH
 docs/VERSION
+docs/GITCOMMIT

hack/RELEASE-CHECKLIST.md

@@ -138,11 +138,10 @@ make AWS_S3_BUCKET=beta-docs.docker.io docs-release
 ### 5. Commit and create a pull request to the "release" branch
 
 ```bash
-export GITHUBUSER="YOUR_GITHUB_USER"
 git add VERSION CHANGELOG.md
 git commit -m "Bump version to $VERSION"
 git push $GITHUBUSER bump_$VERSION
-echo "https://github.com/$GITHUBUSER/docker/compare/dotcloud:master...$GITHUBUSER:bump_$VERSION?expand=1"
+echo "https://github.com/$GITHUBUSER/docker/compare/dotcloud:release...$GITHUBUSER:bump_$VERSION?expand=1"
 ```
 
 That last command will give you the proper link to visit to ensure that you