Install polymer-cli: (Need at least npm v0.3.0)

npm install -g polymer-cli

git clone <project>
cd shop
npm start

npm run serve

polymer test

npm run build

This command serves the minified version of the app in an unbundled state, as it would be served by a push-compatible server:

polymer serve build/unbundled

This command serves the minified version of the app generated using fragment bundling:

polymer serve build/bundled