chore(package): update babel-core to version 6.26.0 (#4096)

Author: greenkeeper[bot]

package.json

@@ -45,7 +45,7 @@
   },
   "devDependencies": {
     "babel-cli": "6.24.1",
-    "babel-core": "6.25.0",
+    "babel-core": "6.26.0",
     "babel-eslint": "^7.1.1",
     "babel-plugin-syntax-flow": "6.18.0",
     "babel-plugin-transform-flow-strip-types": "6.22.0",