nuke deprecated classes and methods
Fixes #334: remove Float and Double Monoid
remove MetricSpace and BKTree
Merge pull request #340 from larsrh/topic/remove-deprecated

nuke deprecated classes and methods
remove superfluous type parameters in Validation#toValidationNel
Merge pull request #347 from larsrh/topic/remove-metricspace

remove MetricSpace and BKTree
Merge pull request #346 from larsrh/topic/remove-float-monoid

remove Float and Double Monoid