added pull_request_review hook (#2)

Signed-off-by: Ernesto Ruy Sanchez <netors@gmail.com>

Author: netors

github_webhook/webhook.py

@@ -110,6 +110,8 @@ def _get_header(key):
     'public': '{sender[login]} publicized {repository[full_name]}',
     'pull_request': '{sender[login]} {action} pull #{pull_request[number]} in '
                     '{repository[full_name]}',
+    'pull_request_review': '{sender[login]} {action} {review[state]} review on pull #{pull_request[number]} in '
+                           '{repository[full_name]}',
     'pull_request_review_comment': '{comment[user][login]} {action} comment '
                                    'on pull #{pull_request[number]} in '
                                    '{repository[full_name]}',