chore(package): update rollup to version 0.67.4

Closes #33

Author: greenkeeper[bot]

package.json

@@ -41,7 +41,7 @@
     "mocha": "^5.0.0",
     "nyc": "^11.0.2",
     "preact": "^8.1.0",
-    "rollup": "^0.59.0",
+    "rollup": "^0.67.4",
     "rollup-plugin-babel": "^3.0.1"
   },
   "bugs": {