Release 0.2.0

#27 and #47: updated README
#28 and #32: adding sbt-matrix and Spark version update 3.1.2->3.2.3 and 3.3.1
#30 and #34: adding code coverage support
#32 and #42: reducing test log noise
#40: making sure that FromDataframeSampleSizer does not create empty samples from non-empty DataFrame

Release 0.1.0

The first release of this library.