Fix to make for tag iterate objects like Shopify liquid.

Ref: https://github.com/Shopify/liquid/wiki/Liquid-for-Designers#allowed-collection-types

tags/for.js

@@ -43,7 +43,7 @@ module.exports = function (liquid) {
         if (_.isString(collection) && collection.length > 0) {
           collection = [collection]
         } else if (_.isObject(collection)) {
-          collection = Object.keys(collection)
+          collection = Object.keys(collection).map((key) => [key, collection[key]])
         }
       }
       if (!Array.isArray(collection) || !collection.length) {

test/tags/for.js

@@ -28,9 +28,9 @@ describe('tags/for', function () {
   })
 
   it('should support object', function () {
-    var src = '{%for key in obj%}{{key}}-{%else%}b{%endfor%}'
+    var src = '{%for item in obj%}{{item[0]}},{{item[1]}}-{%else%}b{%endfor%}'
     return expect(liquid.parseAndRender(src, ctx))
-      .to.eventually.equal('foo-coo-')
+      .to.eventually.equal('foo,bar-coo,haa-')
   })
 
   describe('scope', function () {