Allow for the parallel simulation and comparison of trjs with unique initial conditions.

Updating my branch.  I know I will need to change some networkx stuff, and I think the result file compression handling has changed.  This will impact how the parallel trajectory pickles are recombined.

I also added an isothermal compressibility target a few months ago - it's useless (for now) as the needed sampling is on the order of 100 ns.
Can you check what I have in liquid.py?  I think the first iteration is not always zero because of how we may continue a previous run.