This is an alfred workflow. This means you need Alfred. And you need the alfred powerpack.

This workflow makes it easer to search for development documentation across a wide range of languages and frameworks.

To download a pre packaged workflow, check out the main site: http://wemakeawesomesh.it/alfred-dev-doctor

To create your own parsers for documentation searches, check out
http://www.reddit.com/r/programming/comments/1awtgx/alfredd_workflow_to_help_discover_docs_for/

Happy Hacking :)