Update CHANGELOG.md for release 1.15.0

Update CHANGELOG.md for swift fix of relase 1.14.0.

Merge pull request google#695 from tirodkar/upSwift

Update Swift file and CHANGELOG for 1.13.0 release.

Updating changelog for 1.12.1 release

Bumping version to 1.12.0

Update Cheatsheet and CHANGELOG for 1.11.0

1.10.1 release change log

Final Update for CHANGELOG.md for 1.10.0

Create CHANGELOG.md

Update files for 1.9.3 release