gulp is a devDependency, when it should be a regular or peerDependency

[heikomat]

I'm submitting a bug report

• Library Version:
  0.30.1

Please tell us about your environment:

• Operating System:
  OSX 10.12.6

• Node Version:
  8.9.4

• NPM Version:
  5.6.0

• Browser:
  not important

• Language:
  not important

• Loader/bundler:
  not important

Current behavior:
when installing aurelia-cli, gulp is not installed alongside it, because it is listed in the devDependencies.
running commands like au build doesn't work in that environment, because they require gulp

• What is the expected behavior?
  gulp should be a regular dependency, or at least a peerDependency, because it is required to run commands like au build, and not only for the development of the aurelia-cli.

• What is the motivation / use case for changing the behavior?
  I have a specific postinstall-script that moves and links dependencies depenending on what is mentioned in the package.json of local modules. because of that, and because the aurelia-cli doesn't state gulp as a dependency, the aurelia-cli ends up using a gulp-version of a different local module that is incompatible.

also: the aurelia-commands seem to require gulp version 4.0.0, but version ^3.9.1 is listed in the devDependencies.

[Alexander-Taran]

@JeroenVinke how can this issue be improved to be actionable?