DOC: xray -> xarray

@shoyer just came across this in the docs. These should be the only
(remaining) mentions of xray

Author: Joris Van den Bossche <jorisvandenbossche@gmail.com>

Closes pandas-dev#12419 from jorisvandenbossche/doc-xray and squashes the following commits:

b1f14f8 [Joris Van den Bossche] DOC: xray -> xarray

doc/source/ecosystem.rst

@@ -172,10 +172,10 @@ Geopandas extends pandas data objects to include geographic information which su
 geometric operations. If your work entails maps and geographical coordinates, and
 you love pandas, you should take a close look at Geopandas.
 
-`xray <https://github.com/xray/xray>`__
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+`xarray <https://github.com/pydata/xarray>`__
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-xray brings the labeled data power of pandas to the physical sciences by
+xarray brings the labeled data power of pandas to the physical sciences by
 providing N-dimensional variants of the core pandas data structures. It aims to
 provide a pandas-like and pandas-compatible toolkit for analytics on multi-
 dimensional arrays, rather than the tabular data for which pandas excels.

doc/source/io.rst

@@ -4599,11 +4599,11 @@ into and from pandas, we recommend these packages from the broader community.
 netCDF
 ''''''
 
-xray_ provides data structures inspired by the pandas DataFrame for working
+xarray_ provides data structures inspired by the pandas DataFrame for working
 with multi-dimensional datasets, with a focus on the netCDF file format and
 easy conversion to and from pandas.
 
-.. _xray: http://xray.readthedocs.org/
+.. _xarray: http://xarray.pydata.org/
 
 .. _io.perf: