Allow convertObjectToArray to handle objects with no prototype

Currently this method expects `hasOwnProperty` to exist on the passed object. By using the method on `Object.prototype` instead, objects created with `Object.create(null)` can also be properly handled.

Ran into this bug trying to pass graphQL input objects (heavily uses `Object.create(null)`) directly to hmset commands

Use call

lib/utils/index.js

@@ -169,13 +169,12 @@ exports.timeout = function (callback, timeout) {
  * ```
  */
 exports.convertObjectToArray = function (obj) {
-  var result = [];
-  for (var key in obj) {
-    if (obj.hasOwnProperty(key)) {
-      result.push(key, obj[key]);
+  return Object.keys(obj).reduce(function (array, key) {
+    if (Object.prototype.hasOwnProperty.call(obj, key)) {
+      array.push(key, obj[key]);
     }
-  }
-  return result;
+    return array;
+  }, []);
 };
 
 /**

test/unit/utils.js

@@ -82,6 +82,9 @@ describe('utils', function () {
 
   describe('.convertObjectToArray', function () {
     it('should return correctly', function () {
+      var nullObject = Object.create(null);
+      nullObject.abc = 'def';
+      expect(utils.convertObjectToArray(nullObject)).to.eql(['abc', 'def']);
       expect(utils.convertObjectToArray({ 1: 2 })).to.eql(['1', 2]);
       expect(utils.convertObjectToArray({ 1: '2' })).to.eql(['1', '2']);
       expect(utils.convertObjectToArray({ 1: '2', abc: 'def' })).to.eql(['1', '2', 'abc', 'def']);