v1.2.0

• feat: move to babel-preset-env instead of babel-preset-es2015 (which is deprecated now)
• chore: enable CircleCI integration to check PRs before merge
• chore: setup success build check on CI
• chore bootstrap eslint to enforce code style based on airbnb configuration
• chore: bootstrap test environment using jest
• chore: setup test run on CI
• refactor: update code based on eslint rules (auto-fix)
• chore: add script for release generation
• chore: add script for release note generation