Update version number in package.json

prep for 1.6.0 release (PowerShell#1206)

Merge pull request PowerShell#1099 from PowerShell/rkeithhill/prep-re…

…lease

Prep for 1.5.1 release

Bump version to 1.5.0, update CHANGELOG.md

Bump version to 1.4.3, update CHANGELOG.md

Bump version to 1.4.2, update CHANGELOG.md

Bump version to 1.4.1, update CHANGELOG.md

Bump version to 1.4.0, update CHANGELOG.md

Bump version to 1.3.2, update CHANGELOG.md

Bump version to 1.3.1, update CHANGELOG.md