chore(package): update babel-core to version 6.26.0

Author: greenkeeper[bot]

package.json

@@ -34,7 +34,7 @@
     "through2": "2.0.3"
   },
   "devDependencies": {
-    "babel-core": "6.25.0",
+    "babel-core": "6.26.0",
     "babel-preset-es2015": "6.24.1",
     "del": "3.0.0",
     "eslint": "4.4.1",