Region Adjacency Graph

## Example Images
![figure_1](https://cloud.githubusercontent.com/assets/3823490/3291718/5ce9b952-f587-11e3-8c29-e2aace6d7794.png)
![figure_2](https://cloud.githubusercontent.com/assets/3823490/3291723/7074b134-f587-11e3-8c73-d28222891a21.png)


@vighneshbirodkar additionally, you can generate that report locally (assuming you are running a *nix system) by running `$ make coverage` in the repo root. This is a lot faster than waiting for the Coveralls reports.