version bump 2.1.0

version bump 2.1.0a1

version bump 2.0.3

version bump 2.0.2

version bump 2.0.1

version bump -> 2.0.0

version bump 2.0.0-beta-04

version bump -> 2.0.0-beta-03

updated build-system according to pep517 + added setuptools dependenc…

…y (thx @dvzrv)