* Support minimal dependencies in examples
* bins="auto" only supported for numpy >= 1.11
* viridis is default cmap in matplotlib 2
* Use signature instead of viridis cmap
Use a sparse matrix representation of the neighbors.
Re-factored the QuadTree implementation to avoid insertion errors.
Various fixes in the gradient descent schedule to get the Barnes Hut and exact solvers to behave more robustly and consistently.
TakingItCasual