bots: Add helloworld example bot.

contrib_bots/bots/helloworld/helloworld.py

@@ -0,0 +1,24 @@
+# See readme.md for instructions on running this code.
+
+
+class HelloWorldHandler(object):
+    def usage(self):
+        return '''
+        This is a boilerplate bot that responds to a user query with
+        "beep boop", which is robot for "Hello World".
+
+        This bot can be used as a template for other, more
+        sophisticated, bots.
+        '''
+
+    def handle_message(self, message, client, state_handler):
+        content = 'beep boop'
+
+        client.send_message(dict(
+            type='stream',
+            to=message['display_recipient'],
+            subject=message['subject'],
+            content=content,
+        ))
+
+handler_class = HelloWorldHandler

contrib_bots/bots/helloworld/readme.md

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+Simple Zulip bot that will respond to any query with a "beep boop".
+
+The helloworld bot is a boilerplate bot that can be used as a
+template for more sophisticated/evolved Zulip bots.