Update babel to beta.39 (babel#7302)

Author: hzoo

package.json

@@ -10,18 +10,18 @@
     "test": "make test"
   },
   "devDependencies": {
-    "@babel/cli": "7.0.0-beta.38",
-    "@babel/core": "7.0.0-beta.38",
-    "@babel/preset-env": "7.0.0-beta.38",
-    "@babel/preset-flow": "7.0.0-beta.38",
-    "@babel/preset-stage-0": "7.0.0-beta.38",
-    "@babel/register": "7.0.0-beta.38",
+    "@babel/cli": "7.0.0-beta.39",
+    "@babel/core": "7.0.0-beta.39",
+    "@babel/preset-env": "7.0.0-beta.39",
+    "@babel/preset-flow": "7.0.0-beta.39",
+    "@babel/preset-stage-0": "7.0.0-beta.39",
+    "@babel/register": "7.0.0-beta.39",
     "async": "^1.5.0",
     "babel-eslint": "^8.0.1",
     "babel-loader": "8.0.0-beta.0",
     "babel-plugin-istanbul": "^4.1.4",
     "babel-plugin-transform-charcodes": "0.0.10",
-    "babylon": "7.0.0-beta.38",
+    "babylon": "7.0.0-beta.39",
     "browserify": "^13.1.1",
     "bundle-collapser": "^1.2.1",
     "chai": "^4.1.0",