fleshing out docs a bit
fleshing out docs a bit

jhamman/xarray,jhamman/xarray,jhamman/xarray,kjordahl/xray,kjordahl/xray,rabernat/xray,cpaulik/xray,pydata/xarray,shoyer/xarray,markelg/xray,jcmgray/xarray,jhamman/xray,petercable/xray,chunweiyuan/xarray,xray/xray,rabernat/xray,pydata/xarray,drewokane/xray,cpaulik/xray,NicWayand/xray,markelg/xray,shoyer/xarray,shoyer/xray,markelg/xray,pydata/xarray