Updates release notes.

Author: arokem

CHANGES.rst

@@ -1,3 +1,13 @@
+1.3.1 (February 3rd, 2021)
+==========================
+Fixes a bug in cases where the number of targets is larger than
+the number of samples in each target.
+
+1.3 (December 2, 2020)
+=========================
+This version includes changes to the documentation, to refer to the
+published paper.
+
 1.2.1 (September 22, 2020)
 ==========================
 This micro version fixes a few small things in the documentation.
@@ -24,5 +34,3 @@ Version 1.0 (May 07, 2020)
 
 This is the first major release of the software, in tandem with the appearance
 of the preprint about the method.
-
-