Custom npm install command

[AlMcKinlay]

It would be great if we could define a custom npm install command for apps.

For example, I have an app that I run with guv. However, I don't want it to install the devdependencies (it doesn't need them), so I would like it to run with "npm install --production" to save time and space.

Edit: Version 3.5.17 Node 6.2.2 Npm 3.10.2