Add coordinates encoding test
Add coordinates encoding test

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