Test that using identity matrix for JS embedding layer has no effect on correctness

[Darktex]

The JS code was made to enable training in a browser in reasonable time. This meant that Karpathy added an extra layer before the LSTMs that mapped the vocabulary (of size ~50-100) to a much smaller embedding (the example uses size 5). We won't care about training, so given that we will only do forward propagation we should be able to afford skipping this embedding step, but the JS code expects to find a matrix Wil that contains the weights for the embedding. I have therefore hacked it a bit by setting an embedding size to be the same as the vocabulary size, and setting Wil to be an identity matrix. This needs testing.