Update prop-types dependency

Author: Clauderic Demers

package.json

@@ -49,7 +49,7 @@
     "babel-runtime": "^6.11.6",
     "invariant": "^2.2.1",
     "lodash": "^4.12.0",
-    "prop-types": "^15.5.6"
+    "prop-types": "^15.5.7"
   },
   "peerDependencies": {
     "react": "^0.14.0 || ^15.0.0",