Pygcn

- Add AMON_ICECUBE_EHE notice type. [Leo Singer]

- Add AMON and CALET notice types. [Leo Singer]

- Cleanly shut down server socket. [Leo Singer]

This decreases or eliminates the prevalence of `Address already in use`
errors when the server is killed (e.g. via a `KeyboardInterrupt`) and
immediately restarted.

- Add some log messages. [Leo Singer]

- Update setuptools bootstrap script. [Leo Singer]

- Update setuptools bootstrap script. [Leo Singer]

- Add LIGO/Virgo notice types. [Leo Singer]

- Restore compatibility with Python 2.7.3. [Leo Singer]

Python 2.7.3's io.BytesIO() cannot accept a bytes object, but not a
buffer object.