Reduce amount of climate data by clipping netcdf to glaciers+1000m buffer

[jlandmann]

Start off here:
pydata/xarray#501

[jlandmann]

Okay, I just realised that this is useful for the beginning, but not when we want to calculate catchment runoff. Then it should be cut either to the catchments+buffer (temp gradient calculation!) or the entire data need to be left as they are. The question would be if we want to calculate the runoff of all catchments, not only those with glaciers.

[fmaussion]

See also: http://salem.readthedocs.io/en/latest/examples.html#subsetting-and-selecting-data

[jlandmann]

Thank you so much @fmaussion! You fill the xarray gaps =)