bump version number (2.8.2 -> 2.8.3)

bump version number (2.8.1 -> 2.8.2)

bump version number (2.8.0 -> 2.8.1)

optimize code

bump version number (2.6.2 -> 2.7.0), update dependencies

update 3rd-party dependencies and bump version number

Merge pull request #272 from snshn/new-release

New release (2.6.1)

Merge pull request #265 from snshn/version-bump

Bump version (2.5.0 -> 2.6.0)

Merge pull request #256 from snshn/more-tests-fixes-and-improvements

More tests, fixes, improvements

Merge pull request #251 from snshn/bump-version-again

Bump version number to 2.4.1