Implement universe.numberOfAliveNeighborsOf(), refactor Evolution test descriptions, add test for dead cell becoming alive.

Agreed. I will start thinking of a way to loop once.

I was reading last night about implementing object equality in Ruby objects. The subject of the hash value was very interesting. 

As it stands in javascript [0, 1] != [0, 1]. I imagine this is because it's checking identity? And they are two separate objects.

What I want to do is say:

```coffeescript
for coord in neighboringCoord
  if coord in @currentlyAliveCells
    numberOfAliveNeighbors += 1
```

However the `coord in @currentlyAliveCells` always evaluates to false