Tsne

This is a Torch implementation of t-SNE, a wrapper to Barnes-Hut t-SNE, and a demo with both implementation for visualizing MNIST digits (requires 'mnist' and 'gfx.so'). Both implementations also rely on 'unsup'.

As this is my first ever Torch commit :-), please check carefully whether I didn't introduce anything inconsistent with the rest of the repo, and whether I did the .rockspec file correctly.