"npm run build" fails

[BartRobeyns]

While following the docs on a totally clean system (only npm installed, no global modules), I ran into some errors when running 'npm run build'.
First I got the error
: no such file or directory
which was caused by not having gulp-cli installed

Second, it reported a missing 'webcomponents-lite.min.js', because I hadn't run 'bower install'.

So npm install gulp-cli && bower install seem necessary with the current version. Can you update the readme to add the missing steps?

Thanks,

Bart