New scrollAnchor and observeChildren libraries

Created new jquery.scrollAnchor.js library which adds smooth scroll capabilities for anchor elements with data-scroll-anchor data attributes.

Also added a very simple, non-dependent mutation observer to watch for new anchor tags being added to the page. Created this as a separate library, jquery.observeChildren.js which implements a reusable child observer that can be used at vistaprint as part of the mobile select-fix.js file once available.

Additionally added some simple unit tests for observeChildren and bare bone documentation for scrollAnchor.