Release 0.6.1

Linfa's 0.6.1 release mainly consists of fixes to existing algorithms and the overall crate. The Isotonic Regression algorithm has also been added to linfa-linear.

Improvements and fixes

• Add constructor for LpDist in linfa-nn.
• Add Send + Sync to trait objects returned by linfa-nn, which are now aliased as NearestNeighbourBox.
• Remove anyhow <= 1.0.48 version restriction from linfa.
• Bump ndarray dependency to 0.15
• Fix serde support for LogisticRegression in linfa-logistic.

New algorithms

Isotonic regression fits a free-form line to the training data. Unlike linear regression, which fits a straight line, isotonic regression can result in a much closer fit to the data. The algorithm has been added to linfa-linear.

Mean absolution percentage error (MAPE) is a method of measuring the difference between two datasets, and has been added to the main linfa crate.