completed 165 HARD - simulated ecology

created superclass ForestInhabitant

implemented Tree#step

still working

fixed issues with Forest#adjacent, added tests

implemented get, get_all, made tests

   - also moved symbol into a method, rather than the
     subclass / class variable nonsense I had before

now use Dirt class for empty spaces

trees now plant saplings, implemented event()

fixed #step test

   - also converted tests to expect() syntax

No more nil

implemented Lumberjack logic

Bear logic, yearly stats

stats summary complete

use command line args, ensure always >= lumberjack