chore(package): update rollup to version 2.0.4

Closes #62

Author: greenkeeper[bot]

package.json

@@ -10,7 +10,7 @@
   "devDependencies": {
     "@rollup/plugin-commonjs": "^11.0.1",
     "@rollup/plugin-node-resolve": "^7.0.0",
-    "rollup": "^1.29.0"
+    "rollup": "^2.0.4"
   },
   "scripts": {
     "build": "rollup -c",