Add two developers to documentation

Author: paulromano

docs/source/developers.rst

@@ -10,6 +10,8 @@ Active development of the OpenMC Monte Carlo code is currently led by:
 * `Bryan Herman <https://github.com/bhermanmit>`_
 * `Nick Horelik <https://github.com/nhorelik>`_
 * `Adam Nelson <https://github.com/nelsonag>`_
+* `Jon Walsh <https://github.com/walshjon>`_
+* `Sterling Harper <https://github.com/walshjon>`_
 * `Benoit Forget <http://web.mit.edu/nse/people/faculty/forget.html>`_
 * `Kord Smith <http://web.mit.edu/nse/people/faculty/smith.html>`_
 * `Andrew Siegel <http://www.mcs.anl.gov/about/people_detail.php?id=404>`_