chore(package): update gh-pages to version 2.1.0

Closes #574

Author: greenkeeper[bot]

package.json

@@ -136,7 +136,7 @@
     "extract-text-webpack-plugin": "~3.0.1",
     "file-loader": "^1.0.0",
     "find-root": "^1.0.0",
-    "gh-pages": "^1.0.0",
+    "gh-pages": "^2.1.0",
     "html-webpack-plugin": "^2.30.1",
     "imports-loader": "^0.7.0",
     "istanbul-instrumenter-loader": "3.0.0",