chore(package): update babel-plugin-transform-es2015-modules-umd to version 6.23.0

https://greenkeeper.io/

Author: greenkeeper[bot]

package.json

@@ -60,7 +60,7 @@
     "babel-loader": "6.2.10",
     "babel-plugin-external-helpers": "6.18.0",
     "babel-plugin-istanbul": "3.1.2",
-    "babel-plugin-transform-es2015-modules-umd": "6.18.0",
+    "babel-plugin-transform-es2015-modules-umd": "6.23.0",
     "babel-preset-es2015": "6.18.0",
     "chai": "3.5.0",
     "coveralls": "2.11.15",