Installation fails with NPM 3

[ghost]

Running npm install fails on Node.js >= 5 because NPM v3 doesn't install peerDependencies automatically (https://docs.npmjs.com/files/package.json#peerdependencies).

The dependency requirejs is needed by the project but it's set as a peer dependency.

[natlibfi-arlehiko]

Reopening because this is a valid issue.