Add a .gitignore with initial entries suitable for python.
Incorporate Gazebo protobuf definitions.

This adds both a Makefile rule to re-generate the python protobuf
definitions, as well as the generated definitions for Gazebo 2.2.1.
Initial import of pre-cleaned up network routines.

This includes most of the basic logic behind the publish subscribe
protocol, but some details are omitted, there is very little
documentation, and nothing is tested.
Improve documentation.

 * Convert docstrings to use the triple-double quote notation.
 * Convert all the publicly visible docstrings to use the google python
   docstring conventions.
 * Update __init__.py so that the three primary classes are listed in
   the package level help string.
Further documentation improvements.

 * Add some docstrings to non-exposed classes.
 * Add a TODO on an overly broad "except:" block.
Document a protocol mis-spelling.