Fix neighbor index in island ring model

[ghost]

The ring model is currently crossing over each individual with itself.

I had to stare at this to make sure my eyes weren't deceiving me.

In ModRing Apply():

var (
    indi      = pop.Individuals[i].Clone(pop.RNG)
    neighbour = pop.Individuals[i%len(pop.Individuals)]
)
indi.Crossover(neighbour, pop.RNG)

I guess that's supposed to be (i+1)%len(...)

The PR includes a couple other minor things.

[coveralls]

Pull Request Test Coverage Report for Build 287

• 2 of 2 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 99.631%

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Totals
Change from base Build 286:	0.0%
Covered Lines:	1621
Relevant Lines:	1627

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💛 - Coveralls

[MaxHalford]

LGTM! You made two good catches :). Thanks a lot.