Fix CONTRIBUTING.md link

CONTRIBUTING.md

@@ -1,6 +1,7 @@
 # Contributing
 
 This project adheres to the [Open Code of Conduct][code-of-conduct]. By participating, you are expected to honor this code.
+
 [code-of-conduct]: http://todogroup.org/opencodeofconduct/#GitHub%20Markup/[email protected]
 
 This library's only job is to decide which markup format to use and call out to an external library to convert the markup to HTML (see the [README](README.md) for more information on how markup is rendered on GitHub.com).