Change hillclimb to print_every in terms of generations.
Added trading fitness, which is accumulated return over a sequence of (buy/short, close) periods. Change to use yhat terminology in SR fitness functions.
Add another hack to try to evaluate expressions of great depth.
Reformatting code.
Add cmdline args for gp.py.
Use a single function for running and processing LBYL-style results. Use a system command.