WIP: Volume Source Estimate Visulaization

![vol_viz](https://f.cloud.github.com/assets/647005/716390/ca460f38-df34-11e2-80bd-717e512b6caa.png)

First experiment with visualizing `VolSourceEstimates` using pynax (https://github.com/AlexandreAbraham/pynax). 

One problem seems to be that the T1.mgz dimensions doesn't correspond to the anatomical directions that pynax assumes. @AlexandreAbraham, it seems to me that pynax should use the header info to do this, or is there an other better/easier way to re-orient the data before supplying them to pynax?