add line pointing to xray-data and example ipython notebook in seasonal mean example
add line pointing to xray-data and example ipython notebook in seasonal mean example

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