Update email to sbillinge

Author: cadenmyers13

README.rst

@@ -129,4 +129,4 @@ Before contributing, please read our `Code of Conduct <https://github.com/diffpy
 Contact
 -------
 
-For more information on diffpy.fourigui please visit the project `web-page <https://diffpy.github.io/>`_ or email Prof. Simon Billinge at sb2896@columbia.edu.
+For more information on diffpy.fourigui please visit the project `web-page <https://diffpy.github.io/>`_ or email Prof. Simon Billinge at sbillinge@columbia.edu.