setup.py updates (#3062)
setup.py updates (#3062)

Mark xarray as "Production/Stable" rather than "Beta". Apparently some users
have IT polices prohibiting the use of "beta" software!
jhamman/xray,pydata/xarray,xray/xray,pydata/xarray,jhamman/xarray,shoyer/xarray,markelg/xray,pydata/xarray,jhamman/xarray,markelg/xray,jhamman/xarray,shoyer/xarray,markelg/xray