Doesn't run prepublish hook on npm install

[AlMcKinlay]

When I install an app, it does npm install, but it doesn't run the prepublish hook (which normally runs on npm install). This is used by some npm apps to run a build, and means the build has to be run manually every time it is installed/updated.

Version 3.5.17
Node 6.2.2
Npm 3.10.2