Update __init__.py

Added guard: "# TCP sockets don't have a flush method"

This is a fix for an Exception I got when trying to bind the cli to a TCP socket, using your example code in the readme. I am running Linux 3.2.0 on a Debian-type distro FWIW. Below is the traceback of the Exception this change fixes:

AttributeError                            Traceback (most recent call last)
<ipython-input-8-b320e842537f> in <module>()
      6 s.listen(1)
      7 c, a = s.accept()
----> 8 cli = CLI(c)
      9 while True:
     10     cli.read()

/tmp/cli/__init__.pyc in __init__(self, socket, name, prompt)
     89         self.errors = []
     90         self.is_running = True
---> 91         self.send(self.prompt)
     92 
     93     @property

/tmp/cli/__init__.pyc in send(self, data)
    116         data = '\r\n'.join(RE_NEWLINE.split(data))
    117         self.socket.send(data)
--> 118         if hasattr(self.socket, "flush"):
    119             self.socket.flush()
    120 

AttributeError: '_socketobject' object has no attribute 'flush'