Fix babel-preset-env version

package.json

@@ -20,7 +20,7 @@
     "babel-plugin-transform-class-properties": "^6.24.1",
     "babel-plugin-transform-object-rest-spread": "^6.26.0",
     "babel-plugin-transform-runtime": "^6.23.0",
-    "babel-preset-env": "1.6.1",
+    "babel-preset-env": "^1.6.1",
     "babel-preset-stage-0": "^6.24.1",
     "babel-runtime": "^6.26.0",
     "case-sensitive-paths-webpack-plugin": "^2.1.1",