v2.1.0

Changes

• Cloud SDK release 271.0.0
• Changed default installation path from ~/opt/google-cloud-sdk to
  ~/google-cloud-sdk with backwards compatible detection of the old
  default installation location
• Automatically added blocks in .bashrc and .zshrc do not look for other
  installation paths

Development improvements

• Added Makefile with tasks for development
• Improved Travis CI performance with multiple build stages
• Added GitHub Actions workflow with pre-commit hooks for running linting tasks
  when new code is pushed to the repository
• Added commitlint commit-msg hook
• Fixed bash scripts not working on macOS with BSD sed
• Workaround for ansible-lint installation issue on Travis
• Move bash scripts out of the repository root
• Format shell scripts with shfmt
• Validate shell scripts with shellcheck