You can think of extprot as something akin to Google's protocol buffers,
with a few extra bytes of serialisation overhead and a Python binding
that doesn't have nearly as many rough edges. For example:
* It's a stand-alone python module, packaged and distributed in
the standard fashion.
* It's friendly to dynamic package management tools like pip.
* It works exclusively with standard Python objects. Declared a
list field? It's a native list object.
* You don't need to compile your protocol definitions.