How to cleanly stop a reactor?

Nobody has claimed this yet.

I'm trying to write an asynchronous client that's just trying to connect, join a channel, send a message and then quit. I looked at irccat as an example, but I am left with a reactor working while I want the rest of my program to continue outside of that flow. My workaround is that I created a multiprocessing.Process that I then terminate:

```
import time
import logging
import multiprocessing

import irc.client

logging.basicConfig(level='DEBUG')

def notify_thread(msg):
client = irc.client.Reactor()
server = client.server()
server.connect('irc.freenode.net', 6667, 'hsldzat')

def on_connect(connection, event):
connection.join('##test3')

def on_join(connection, event):
connection.privmsg('##test3', msg)
connection.quit()

client.add_global_handler("welcome", on_connect)
client.add_global_handler("join", on_join)
client.process_forever()

def notify(msg):
t = multiprocessing.Process(target=notify_thread, args=(msg, ))
t.start()
time.sleep(60)
t.terminate()

while True:
for i in range(3):
notify('hello' + str(i+1))
```

Assuming that it's critical for my code to work synchronously and outside of the callback-based model, is there a cleaner way to use the API? Perhaps it would make sense to incorporate it into irccat example instead of doing sys.exit()?

Start with the irccat example and the Reactor, server connection, callback handlers, and process_forever calls shown in the issue. Determine how a client can stop the reactor cleanly after sending its message while allowing synchronous code to continue, and document or expose an API whose completion can be verified without terminating a process.

Written by the indexing model from the issue text.