fix(package): update rollup to version 2.11.2

Closes #66

Author: greenkeeper[bot]

package.json

@@ -28,7 +28,7 @@
   "private": true,
   "dependencies": {
     "lerna": "^3.13.0",
-    "rollup": "^1.27.9"
+    "rollup": "^2.11.2"
   },
   "devDependencies": {
     "@babel/cli": "^7.7.4",