Add support for the new channels API

examples/channels.py

@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals, print_function
+import frida
+
+
+device = frida.get_usb_device()
+
+channel = device.open_channel("tcp:21")
+print("Got channel:", channel)
+
+welcome = channel.read(512)
+print("Got welcome message:", welcome)
+
+channel.write_all(b"CWD foo")
+reply = channel.read(512)
+print("Got reply:", reply)
+
+channel.close()
+print("Channel now:", channel)