code: function findLinksOutward( node, graph ) {
      var children = [];
  
      for( var i = 0; i < graph.length; i++ ) {
        if( node == graph[i].source ) {
          children.push( graph[i] );
        }
      }
  
      return children;
    }
docs: /* Given a node, find all links for which this is a source
  in the current 'known' graph