Ensure _.clone and _.cloneDeep work on prototype objects.

lodash.js

@@ -4956,6 +4956,9 @@
      * @returns {Object} Returns the initialized clone.
      */
     function initCloneObject(object) {
+      if (isPrototype(object)) {
+        return {};
+      }
       var Ctor = object.constructor;
       return baseCreate(isFunction(Ctor) ? Ctor.prototype : undefined);
     }