Add moved diff into its own directory

Author: mattphillips

src/index.js renamed to src/diff/index.js

@@ -1,4 +1,4 @@
-import { isEmpty, isObject } from './utils';
+import { isEmpty, isObject } from '../utils';
 
 const diff = (lhs, rhs) => {
  if (lhs === rhs) return {}; // equal return no diff