Fix docstring indentation in regression.py.

Also use print function so my linter stops complaining at me.
Save final simulation data under "final/" namespace in HDFStore.
Initial docs on the UrbanSim simulation framework.

[ci skip]
Document class attributes in urbansim.sim.simulation

[ci skip]
Make _TableSourceWrapper a private class.
Merge pull request #88 from synthicity/sim-docs

Simulation framework documentation