v0.4.0 - 2021-01-27

This release introduces a few changes to optimize processing speed by re-implementing
the Gaussian KDE pdf to use vectorized root finding methods and also adding the option
to subsample the data during univariate selection.

General Improvements

• Make gaussian_kde faster - Issue #200 by @k15z and @fealho
• Use sub-sampling in select_univariate - Issue #183 by @csala