chore(package): update rollup to version 2.0.1

Closes #48

Author: greenkeeper[bot]

package.json

@@ -17,7 +17,7 @@
   "devDependencies": {
     "ava": "^2.0.0",
     "jsdom": "^14.0.0",
-    "rollup": "^1.1.1",
+    "rollup": "^2.0.1",
     "rollup-plugin-commonjs": "^10.0.0",
     "rollup-plugin-node-resolve": "^5.0.0",
     "standard": "^14.3.0"