support github pull request labels

Allow to match trigger on adding or removing github labels. Also
reporter can add or remove labels.

Change-Id: Id385b92590e252c283ba3ebe1ecfd33b34469a2e
Co-Authored-By: Jesse Keating <omgjlk@us.ibm.com>
diff --git a/doc/source/reporters.rst b/doc/source/reporters.rst
index ced3b78..e3ab947 100644
--- a/doc/source/reporters.rst
+++ b/doc/source/reporters.rst
@@ -55,6 +55,16 @@
   merge the pull reqeust. Defaults to ``false``.
   ``merge=true``
 
+  **label**
+  List of strings each representing an exact label name which should be added
+  to the pull request by reporter.
+  ``label: 'test successful'``
+
+  **unlabel**
+  List of strings each representing an exact label name which should be removed
+  from the pull request by reporter.
+  ``unlabel: 'test failed'``
+
 SMTP
 ----