chore(package): update react-test-renderer to version 15.6.1

Author: greenkeeper[bot]

package.json

@@ -123,6 +123,6 @@
     "prettier": "1.4.4",
     "react-native-mock": "0.3.1",
     "react-native-view-shot": "1.9.1",
-    "react-test-renderer": "15.5.4"
+    "react-test-renderer": "15.6.1"
   }
 }