breeding logic

[joshuavial]

when two kiwis breed, not only is the gen of the chick one higher than the highest gen kiwi, the stats are weaker (with a bit of randomness to keep things interesting)

[harrison-symes]

https://github.com/dev-academy-programme/plug-cryptokiwis/blob/react/createKiwi.js
@joshuavial This was my original attempt at breeding logic. Variance, but wieghts are based on parents stats