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 Y2Z#272 from snshn/new-release

New release (2.6.1)

Merge pull request Y2Z#265 from snshn/version-bump

Bump version (2.5.0 -> 2.6.0)

Merge pull request Y2Z#256 from snshn/more-tests-fixes-and-improvements

More tests, fixes, improvements

Merge pull request Y2Z#251 from snshn/bump-version-again

Bump version number to 2.4.1

Merge pull request Y2Z#233 from snshn/cargo-fix-license-identifier

Fix license identifier in Cargo.toml

Merge pull request Y2Z#207 from snshn/bump-version

bump version (2.3.0 -> 2.3.1)