Update some details on building from the git repository and building the Python API.
Rationalize location of implementation of game tree-specific objects.
Fix external Nash solver in Python to use revised Game.write() interface.
Improvements to gametracer from the group at UBC.

* Add a verbose option for gambit-ipa
* Fix a bug in the gametracer implementation of ipa where division
  by zero was possible.
* Correct payoff calculations in gametracer's game representation.
Update version number and copyright date spans.
Merge branch 'master' into agg