chore(package): update rollup to version 0.39.2

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -35,7 +35,7 @@
     "underscore": "1.8.3",
     "jsdoc-to-markdown": "^2.0.1",
     "markdown-doctest": "^0.9.1",
-    "rollup": "^0.39.1"
+    "rollup": "^0.39.2"
   },
   "contributors": [{
     "name": "Torsten Link",