fix(package): update rollup to version 2.1.0

Closes #545

Author: greenkeeper[bot]

package.json

@@ -83,7 +83,7 @@
     "pascal-case": "^2.0.1",
     "prettier": "^1.19.1",
     "progress-estimator": "^0.2.2",
-    "rollup": "^1.32.1",
+    "rollup": "^2.1.0",
     "rollup-plugin-babel": "^4.3.2",
     "rollup-plugin-sourcemaps": "^0.4.2",
     "rollup-plugin-terser": "^5.1.2",