Refactor: Make StateHandler() function independent.

This refactor makes the nested class 'StateHandler' in the
file /contrib_bots/bot_lib.py independent class. It previously
was nested in 'run_message_handler_for_bot' function.

This is done to write a cleaner test file for contrib_bots using
mock library.

contrib_bots/bot_lib.py

@@ -71,6 +71,16 @@ class BotHandlerApi(object):
                 content=response,
             ))
 
+class StateHandler(object):
+    def __init__(self):
+        self.state = None
+
+    def set_state(self, state):
+        self.state = state
+
+    def get_state(self):
+        return self.state
+
 def run_message_handler_for_bot(lib_module, quiet, config_file):
     # Make sure you set up your ~/.zuliprc
     client = Client(config_file=config_file)
@@ -78,16 +88,6 @@ def run_message_handler_for_bot(lib_module, quiet, config_file):
 
     message_handler = lib_module.handler_class()
 
-    class StateHandler(object):
-        def __init__(self):
-            self.state = None
-
-        def set_state(self, state):
-            self.state = state
-
-        def get_state(self):
-            return self.state
-
     state_handler = StateHandler()
 
     if not quiet: