chore(package): update react to version 15.5.4

https://greenkeeper.io/

package.json

@@ -19,7 +19,7 @@
     "url": "git+ssh://git@github.com/LLK/scratch-gui.git"
   },
   "peerDependencies": {
-    "react": "15.x.x",
+    "react": "^15.5.4",
     "react-dom": "^15.5.4"
   },
   "devDependencies": {
@@ -66,7 +66,7 @@
     "svg-to-image": "1.1.3",
     "svg-url-loader": "2.0.2",
     "travis-after-all": "^1.4.4",
-    "webpack": "2.4.1",
+    "webpack": "^2.4.1",
     "webpack-dev-server": "^2.4.1",
     "xhr": "2.4.0"
   }