Optional arbor.js

Neo4's Data Browser uses arbor.js for the graph visualization. Unfortunately it doesn't work in IE7 or IE8. 

This PR incorporates a primitive check for browser version, coupled with a requirejs plugin called featrurejs to load alternate module implementations. For the Data Browser, there is a fake implementation of arborjs which reports that it is dysfunctional, causing the rendered view to include an apology about being unable to render instead of trying to render and failing.

CSS styling included.