Updated minimum scipy version to 0.13

Our scipy.io.netcdf related tests appear to fail on scipy==0.11. I'm not sure
if scipy==0.12 works, but scipy==0.13 certainly works. So for now (to avoid
future issues), I've updated the dependencies in our setup.py file.
Merge pull request #38 from akleeman/update-listed-dependences

Updated minimum scipy version to 0.13