Polymorphism example code

In [polymorphism.jl](https://github.com/benmoran/TensorFlow.jl/blob/master/examples/polymorphism.jl#L47), should the following code:

``` julia
for i in 1:batch_size
  y_one_hot[y, i] = 1.
end
```

instead be:

``` julia
for i in 1:batch_size
  y_one_hot[y[i], i] = 1.
end
```

? I'm trying to see if I understand the example correctly.
