chore(vendor): update jsoniter package (#1033)

vendor/vendor.json

@@ -34,10 +34,10 @@
 			"revisionTime": "2017-06-01T23:02:30Z"
 		},
 		{
-			"checksumSHA1": "WFJPa8cL6nzQU3yA1iN+gmaqrSU=",
+			"checksumSHA1": "0e59uuETpidkmpaRwipQ8auqwhM=",
 			"path": "github.com/json-iterator/go",
-			"revision": "4b33139ad07fda872cb378bb4218b2fab74ce62b",
-			"revisionTime": "2017-07-12T09:56:51Z"
+			"revision": "6b6938829d6156d7b9825f83eec757f0f571c981",
+			"revisionTime": "2017-07-18T14:19:52Z"
 		},
 		{
 			"checksumSHA1": "9if9IBLsxkarJ804NPWAzgskIAk=",