Fixes Pinball domain

Fix some inconsistencies with RL-Glue. Add the ability
to replay saved trajectories.
Add example experiment for the Pinball domain

This example shows how to use the special TrajectoryRecorder
decorator for saving trajectories. Furthermore, it uses
IPython parallel to compute the performance of many agents
in parallel.

It can be used over a guerilla SSH cluster over the computers in your
lab, or more cleanly on an MPI, PBS or AWS cluster.

For local parallel computation, execute in a separate tab:
$ ipcluster start -n 4

followed by
$ python learn-flat-policy.py -a 100 -n 100 pinball_simple_single.cfg