mutate() must skip elitist genomes

[egtzori]

neataptic version: 1.4.7
As commented in the source (neat.js)
// Elitist genomes should not be included
but code on next line does
for (var i = 0; i < this.population.length; i++) {

(includes elitist genomes to roll for mutation)
Fixing this improves network performance for me.

I will create a pull request to patch this