code: function buildGraph() {
  	const graph = {};
  	// https://jsperf.com/object-keys-vs-for-in-with-closure/3
  	const models = Object.keys(conversions);
  
  	for (let len = models.length, i = 0; i < len; i++) {
  		graph[models[i]] = {
  			// http://jsperf.com/1-vs-infinity
  			// micro-opt, but this is simple.
  			distance: -1,
  			parent: null
  		};
  	}
  
  	return graph;
  }
docs: /*
  This function routes a model to all other models.
  
  all functions that are routed have a property `.conversion` attached
  to the returned synthetic function. This property is an array
  of strings, each with the steps in between the 'from' and 'to'
  color models (inclusive).
  
  conversions that are not possible simply are not included.