Release 0.5.1

Linfa's 0.5.1 release fixes errors and bugs in the previous release, as well as removing useless trait bounds on the Dataset type. Note that the commits for this release are located in the 0-5-1 branch of the GitHub repo.

Improvements

• remove Float trait bound from many Dataset impls, making non-float datasets usable
• fix build errors in 0.5.0 caused by breaking minor releases from dependencies
• fix bug in k-means where the termination condition of the algorithm was calculated incorrectly
• fix build failure when building linfa alone, caused by incorrect feature selection for ndarray