Chromosome.py saves CWD.

Importing PySCeS and StochPy both change the CWD to their module path. Script now saves CWD before importing and changes the CWD in constructor.
Made population accessible to simulation script.

Interface previously returned info about population but now returns a reference to the population. Simulation records genotype, initial parameters, and best fit per generation.
Simulation runs genetic algorithm.

Will output data to log once chromosome.py implements tempfiles.
Added utils to directory so genetic algorithm can reach it.