bump version to 2.0.0b3, update changelog.rst

Bump version to 2.0.0b2

Bump version to 2.0.0b1. Update changelog.

Bump version to 2.0.0b0

Bump version to 1.6.0

Bump version to 1.5.3, update changelog

Bump version to 1.5.2, update changelog

Bump version to 1.5.1, update release notes

bump version to 1.5.0!

Bump version to 1.4.4, update changelog in preparation for release.