Slow down human eating

[bcvery1]

Currently humans eat too much and die too quickly. The rate of eating needs to be reduced to keep them alive longer

[bcvery1]

How to:

• Change food property of struct pen to float64 instead of int
• Create a const eatRate float64, need trial and error to get this right, but start at 0.3
• In the method pen.Eat reduce by len(pen.humans) * eatRate