Summer release
- emd* and sinkhorn* are now performed in parallel for multiple target distributions
- emd and sinkhorn are for OT matrix computation
- emd2 and sinkhorn2 are for OT loss computation
- new notebooks for emd computation and Wasserstein Discriminant Analysis
- relocate notebooks
- update documentation
- clean_zeros(a,b,M) for removimg zeros in sparse distributions
- GPU implementations for sinkhorn and group lasso regularization