[AngularJS] Sane, scalable Angular apps are tricky, but not impossible.

Read from https://medium.com/@bluepnume/sane-scalable-angular-apps-are-tricky-but-not-impossible-lessons-learned-from-paypal-checkout-c5320558d4ef

• ng-Controller is bad, use directive instead.
• Don't specfiy controller in Route, use directive in template.
• Alwasy use an isolated scope
• Use factory only, forget about service and providor
• $expectionHandler
• use angular-ui-router
• Aviod lazy loading ? ? ?