This is the ffExtension add-on.  It contains:

* A program (lib/main.js).
* A few tests.
* Some meager documentation.

Building/running from this directory:

 - Setup environment: 
     `pushd <repo root>/tools/addon-sdk-1.3 && source bin/activate && popd`
 - Run the extension: 
     `cfx run -profile ../devProfile`

See `cfx docs` for more details on the add-on build tool.