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)


This needs to be one line. How about:
```
"""Create edge in `g` between first elem of `values` and rest.
```
(expand "elem" to "element" if it fits, and then expand "rest" to "the rest" if that fits.)