Restore handling of dtype=object arrays in encode_cf_variable
Restore handling of dtype=object arrays in encode_cf_variable

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