Add abandoned module warning.

Author: juseg

README.rst

@@ -1,10 +1,18 @@
+.. Copyright (c) 2013--2018, Julien Seguinot <seguinot@vaw.baug.ethz.ch>
+.. GNU General Public License v3.0+ (https://www.gnu.org/licenses/gpl-3.0.txt)
+
 iceplotlib
 ==========
 
+**Warning:** This package is abandoned and no longer maintained. Much of its
+features have a similar and more versatile implementation in the vastly more
+powerful xarray_.
+
 A plotting library for `PISM`_ using `matplotlib`_ and `netcdf4-python`_.
 
 .. links
 
 .. _netcdf4-python: http://unidata.github.io/netcdf4-python/
 .. _matplotlib: http://matplotlib.org
 .. _PISM: http://www.pism-docs.org
+.. _xarray: http://xarray.pydata.org