Add initial Entity struct/class.
Correctly create consts for number of genes vs number of values for
genes.
Make genome public in Entity.
Make the range for genome values correct.

From 0 to 7 instead of 0 to 8 (too many).
Implement turning the genome into code.
Add some slight documentation for the methods.
Implement mutation.
Make mutate rate a parameter.
Return error if mutate rate is outside of the valid range.
Add test for Entity mutation.
Change mutate rate for testing to 0.9.

Brings less randomness into the equation.
Add implementation and test for crossover.

Does not work for an odd number of genes.
Change number of genes to be a parameter.
Test both even/odd gene numbers for crossover.