chore(package): update surge to version 0.21.3

Closes #41

Author: greenkeeper[bot]

package.json

@@ -57,7 +57,7 @@
     "open": "0.0.5",
     "rimraf": "2.6.1",
     "style-loader": "^0.16.1",
-    "surge": "^0.19.0",
+    "surge": "^0.21.3",
     "webpack": "^2.3.3",
     "webpack-dev-middleware": "^1.10.1",
     "webpack-hot-middleware": "^2.18.0",