watchify events in makefile

Hi,

I have a build setup using `Makefile`, it works great, and it's less headache than other build tools for my taste.

I use also `watchman-make` for other resources in my `Makefile`, and it has a nice feature to call a task when it find a change

```shell
watchman-make -p 'src/backend/app/views/**/*.tmpl' -t templates -p 'src/backend/app/**/*.go' 'src/backend/main.go' -t run
```
both `template` and `run` are tasks that get called when there is a a change in the watched folders.

Is there a way to achieve the same using `watchify` on command line? maybe

```shell
$ watchify -t babelify -e app.js -o app.min.js --on-update-task setup
```
where `setup` is `make` task.

Thanks!