Adapter assignments

• Intoruced a standard Angular-way mechanism for Adapter assignments via $parse service.
• Adapter public methods and properties are extracted into a stand-alone entity which is accessible outside the ui-scroll directive (instead of passing the original ui-scroll Adapter object with all of it's props and methods).
• Fixed Chrome Scroll Anchoring enforced feature bug.
• Added "dev" npm script which is a concurrently combination of dev-server and tests continuous running.