updated SetStrategyAgent documentation.
added stochastic games RandomAgent
Added HashedAggregator datastructure for keeping real valued counts
associated with different keys
added a simple constant state generator for stochastic games.
Added an interface from stochastic games agent to single agent learning
algorithms so that any single agent learnign algorithm can be trivially
used for a stochastic games agent.
Added thread join to RLGlue interface to ensure synchronization between
episodes of an RLGlue interaction.