Compatibility changes

I'm not sure if you accept pull requests, but in my attempts to get Seaborn to work with Python 3 I had to make some modifications to Moss as well. The locator module doesn't work in Python 3 due to nipype not supporting it however all other tests pass on Python 3. 

I also don't have the correct setup to test the locator module in Python 2 but these changes don't introduce any regressions for the other modules.