Bump version to 4.2.2

Bump version to 4.2.1

bump version to 4.2.0

Bump version to 4.1.0

Bump version to 4.0.0

Bump version to 3.2.1

Bump version to 3.2.0

Merge pull request #404 from kishikawakatsumi/swift42

Improve Swift 4.2 compatibility

Merge pull request #376 from kishikawakatsumi/xcode9.3-swift4.1

Xcode9.3 swift4.1

Merge pull request #347 from kishikawakatsumi/release_310

Bump version to 3.1.0