Adding path_as_pattern for netcdf

[jsignell]

Still need to add in a version check for xarray or pin the version higher than 0.11.2 to ensure that encoding['source'] exists.

[jsignell]

Note discussion ongoing at pydata/xarray#2550

[jsignell]

This might get subsumed by #25.

[jsignell]

Closes #30

[martindurant]

Dask project repos tend to do something like

bash miniconda.sh -b -p $HOME/miniconda
export PATH="$HOME/miniconda/bin:$PATH"
conda config --set always_yes yes --set changeps1 no
conda update conda

conda create -n test python=3.6 pytest
source activate test
conda install -c conda-forge ...

[jsignell]

closes #35

[jsignell]

I'm going to merge this if it passes. I think it is sane and good.

[martindurant]

Glad to hear it!