Move push notifications to a consistent subject.

(imported from commit 3b4acb39bbf564625e3c009f4f875da596a7a7ac)

tools/post-receive

@@ -81,7 +81,7 @@ def send_bot_message(oldrev, newrev, refname):
     message_data = {
         "type": "stream",
         "stream": "test" if refname == "refs/heads/test-post-receive" else "devel",
-        "subject": "push-" + new_head,
+        "subject": u"deploy \u21D2 " + branch,
         "content": message,
         "recipient": "tabbott@humbughq.com",
     }