update package version of babel-core

Author: imnot2

package.json

@@ -11,7 +11,7 @@
   "author": "Ruan Yifeng",
   "license": "MIT",
   "dependencies": {
-    "babel-core": "~6.0.20",
+    "babel-core": "~6.8.0",
     "babel-loader": "~6.0.1",
     "babel-preset-es2015": "~6.0.15",
     "babel-preset-react": "~6.0.15",