Anderson acceleration, a few changes in epsilon scheduling, segment sinkhorn divergence

In this new release:

• Anderson acceleration implemented for Sinkhorn.
• Simplifications of the way epsilon scheduling is now defined. the init value should be understood as a multiple of the scale parameter, if one has been passed.
• Addition of segment_sinkhorn_divergence, a convenient way to compute several sinkhorn divergences of various subsets of points in two point clouds X, Y.