add a README w/ a sample on running w/ twisted.

README.md

@@ -0,0 +1,33 @@
+adtwist
+=======
+
+This is a wrapper around the python module
+[alarmdecoder](https://github.com/nutechsoftware/alarmdecoder) that
+makes it compatible w/ the twisted framework.  This replaces the
+included device so that you don't have to use a thread to handle I/O
+from the device.
+
+Currently it is only tested w/ a AD2USB via a serial port.  There is
+no USB auto detect code included.
+
+
+Sample Usage
+------------
+
+Sample code:
+```
+from adtwist import adtwist
+from twisted.internet import reactor
+
+def msgcbfun(ad, message):
+	print 'received msg:', `message`
+
+ad = adtwist('/dev/ttyU1', baudrate=115200)
+ad.on_message += msgcbfun
+
+reactor.run()
+```
+
+This will create an AlarmDecoder instance (from alarmdecoder) and attach
+it to the device `/dev/ttyU1`.  It will print each message received from
+the device.