chore(package): update babel-plugin-transform-regenerator to version …

…6.21.0

Closes graphql#68

https://greenkeeper.io/

package.json

@@ -67,7 +67,7 @@
     "babel-plugin-transform-es2015-template-literals": "6.8.0",
     "babel-plugin-transform-flow-strip-types": "6.18.0",
     "babel-plugin-transform-object-rest-spread": "6.16.0",
-    "babel-plugin-transform-regenerator": "6.16.1",
+    "babel-plugin-transform-regenerator": "6.21.0",
     "chai": "3.5.0",
     "chai-subset": "1.3.0",
     "codemirror": "5.20.2",