Commitizen

Fix

- **commands/bump**: use `return_code` in commands used by bump
- **commands/commit**: use return_code to raise commit error, not stderr

Refactor

- **cmd**: add return code to Command

Fix

- **bump**: add changelog file into stage when running `cz bump --changelog`

Fix

- Raise NotAGitProjectError only in git related command

Feat

- **cli**: enable displaying all traceback for CommitizenException when --debug flag is used

Refactor

- **exception**: rename MissingConfigError as MissingCzCustomizeConfigError
- **exception**: Rename CommitFailedError and TagFailedError with Bump prefix
- **commands/init**: add test case and remove unaccessible code
- **exception**: move output message related to exception into exception
- **exception**: implement message handling mechanism for CommitizenException
- **cli**: do not show traceback if the raised exception is CommitizenException
- introduce DryRunExit, ExpectedExit, NoCommandFoundError, InvalidCommandArgumentError
- use custom exception for error handling
- **error_codes**: remove unused NO_COMMIT_MSG error code

Fix

- **changelog**: empty lines at the beginning of the CHANGELOG