nucleotides test and example in coffeescript

I squashed the commits together into one and renamed the main file. I think I have done everything correctly, but if there is something else let me know :)
> Could you show me?

No problem; it turns out, the condition needed to be `if nucleotide not of @nucleotideCounts` since we are dealing with an object vs. an array (`in` works on arrays as it is wrapping `indexOf`).

https://github.com/wilmoore/xcoffeescript/blob/skip-tests-after-first/nucleotide-count/example.coffee#L13