Add missing attribute to tax rate fixtures

Author: leandrost

spec/fixtures/responses/tax_rates.json

@@ -7,6 +7,7 @@
     "tax_rate_type": "sales_invoice",
     "show_tax": true,
     "active": true,
+    "country": null,
     "created_at": "2015-12-23T07:43:17.881Z",
     "updated_at": "2015-12-23T07:43:17.881Z"
   },
@@ -18,6 +19,7 @@
     "tax_rate_type": "sales_invoice",
     "show_tax": true,
     "active": true,
+    "country": null,
     "created_at": "2015-12-23T07:43:17.890Z",
     "updated_at": "2015-12-23T07:43:17.890Z"
   },
@@ -29,7 +31,8 @@
     "tax_rate_type": "sales_invoice",
     "show_tax": true,
     "active": true,
+    "country": null,
     "created_at": "2015-12-23T07:43:17.897Z",
     "updated_at": "2015-12-23T07:43:17.897Z"
   }
-]
+]