Adding tests for BinDiesel

**TODO**:

- [x] Finish `--help` flag tests
- [x] Implement `opts_description` tests
- [x] Implement `opts_required` tests
- [x] Implement `opts_accessor` tests
- [x] Implement `--dry-run` tests
- [x] Implement `--verbose` tests
- [x] Implement `post_initialize` tests
- [x] Implement `message` tests
- [x] Implement `info_message` tests
- [x] Implement `error_message` tests
- [x] Implement `dry_run?` tests