* add note about how to install rev6 (dfu-util)
* include instructions on installing dfu-util on macOS
```
brew rm avr-gcc
brew rm dfu-programmer
+brew rm dfu-util
brew rm gcc-arm-none-eabi
brew rm avrdude
brew install avr-gcc
brew install dfu-programmer
+brew install dfu-util
brew install gcc-arm-none-eabi
brew install avrdude
```
brew update
brew install avr-gcc@7
brew install dfu-programmer
+ brew install dfu-util
brew install gcc-arm-none-eabi
brew install avrdude
make planck/rev4:default
+Install examples:
+
+ make planck/rev6:default:dfu-util
+
See [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) then the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information.