chore: Bump minimum required version of babylon

Fixes #795

Author: tmcw

package.json

@@ -18,7 +18,7 @@
     "babel-traverse": "^6.16.0",
     "babel-types": "^6.16.0",
     "babelify": "^7.3.0",
-    "babylon": "^6.11.4",
+    "babylon": "^6.17.2",
     "chalk": "^1.1.1",
     "chokidar": "^1.2.0",
     "concat-stream": "^1.5.0",