Visualize token latent factors in 3-dimensional space

[medvedev1088]

Latent factors for tokens produced by the recommender can be visualized in 3D space.

2 things to try here:

1. Change the latent factors to 3 here https://github.com/blockchain-etl/token-recommender/blob/master/wals_ml_engine/trainer/model.py#L43. Then use some visualization tool and see if the tokens are clustered in 3D space.

2. Look into TensorBoard Embedding projector. An example of visualizing embedding of MNIST hand written digits https://www.youtube.com/watch?v=gDQfqRUyfBw, https://projector.tensorflow.org/