fix(package): update apollo-client to version 2.6.4

Closes #570

Author: greenkeeper[bot]

package.json

@@ -49,7 +49,7 @@
     "accepts": "^1.3.4",
     "antd": "3.8.4",
     "apollo-cache-inmemory": "1.6.3",
-    "apollo-client": "2.6.3",
+    "apollo-client": "2.6.4",
     "apollo-link": "1.2.5",
     "apollo-link-error": "^1.0.9",
     "apollo-link-http": "1.5.14",