Add a twisted ‘mllp’ plugin and a simple default receiver.

Allow receiver to specify error handling for text codec errors.
Install twisted mllp plugin.

This seems to be the accepted mechanism, discussed here:

https://mail.python.org/pipermail/distutils-sig/2011-September/018031.html

And here:
http://stackoverflow.com/questions/7275295/how-do-i-write-a-setup-py-for-a-twistd-twisted-plugin-that-works-with-setuptools

The monkey patch is no longer necessary with pip:
https://github.com/pypa/pip/issues/355

Installation will result in a warning which can be ignored:
“package init file 'twisted/plugins/__init__.py' not found (or not a regular file)”