refine node-sass version

package.json

@@ -64,7 +64,7 @@
     "function-bind": "1.1.0",
     "html-webpack-plugin": "2.28.0",
     "http-proxy-middleware": "0.17.3",
-    "node-sass": "4.5.2",
+    "node-sass": "^4.5.0",
     "opn": "4.0.2",
     "optimize-css-assets-webpack-plugin": "1.3.0",
     "ora": "1.1.0",