update changelog

Author: sbillinge

CHANGELOG.rst

@@ -3,3 +3,13 @@ Release notes
 =============
 
 .. current developments
+
+1.0.0
+=====
+
+**Fixed:**
+
+* Change "diffpy.srxplanargui" from python 2 to python 3 architecture.
+* Support ``scikit-package`` Level 5 standard (https://scikit-package.github.io/scikit-package/).
+* Change documentation for diffpy.srxplanargui to successfully display.
+