Fix example git tag command in docs

Author: necolas

CONTRIBUTING.md

@@ -171,6 +171,6 @@ cutting new releases.
    added to the CHANGELOG (inc. date), and edited in the README,
    `component.json`, and `normalize.css` files.
 3. The commit message must be of `v0.0.0` format.
-4. Create an annotated tag for the version: `git tag -m v0.0.0`.
+4. Create an annotated tag for the version: `git tag -m "v0.0.0" v0.0.0`.
 5. Push the changes and tags to GitHub: `git push --tags origin master`
 6. Checkout the `gh-pages` branch and follow the instructions in the README.