chore(package): update babel-loader to version 8.0.4

Closes #59

Author: greenkeeper[bot]

package.json

@@ -57,7 +57,7 @@
   },
   "devDependencies": {
     "babel-core": "6.21.0",
-    "babel-loader": "6.2.10",
+    "babel-loader": "8.0.4",
     "babel-plugin-external-helpers": "6.18.0",
     "babel-plugin-istanbul": "3.1.2",
     "babel-plugin-transform-es2015-modules-umd": "6.18.0",