DuckDuckHack (Docs) - Should use local repo clone as source dir when present

[moollaza]

Currently when making changes to the DuckDuckGo-Documentation repo, there is no easy way to preview your changes as Publisher doesn't check locally for a clone of the repo to use as the source, rather it clones the master branch of the documentation repo into the Publisher cache (~/.publisher) and uses that as the source:
https://github.com/duckduckgo/duckduckgo-publisher/blob/master/lib/DDG/Publisher/Site/Duckduckhack/Root.pm#L51

This unfortunately means you can only preview the current state of the Documentation repo, which isn't very helpful. It should first check for a local clone of the Documentation repo so developers can easily preview their changes like they are able to do with the DuckPAN Server for Spice and Goodies.