dynamixel_pro_controller: 0.8.4-0 in 'hydro/distribution.yaml' [bloom]

Increasing version of package(s) in repository `dynamixel_pro_controller` to `0.8.4-0`:

- distro file: `hydro/distribution.yaml`
- bloom version: `0.5.2`
- previous version for package: `0.8.3-0`

## dynamixel_pro_controller

```
* Added support for YAML-CPP 0.5+.
```