ENH: Add Travis

Travis builds pass, see below, and coveralls has coverage info.

Getting Travis to work required moving the `example_data` (~2.8 MB) into the package (as `surfer/data`), which I think is a welcome change anyway. I also fixed a few `pep8` issues.

Also, the `fsaverage_min.tar.gz` file is currently hosted on my space at UW, which is *not* a tenable long-term solution. @mwaskom do you have somewhere you could host it? If not, @agramfort would it be possible to upload it to Martino's space somewhere? It's <30MB.