Update rollup to the latest version 🚀 (#2161)

* chore(package): update rollup to version 0.68.1

* chore(package): update lockfile package-lock.json

Author: greenkeeper[bot]

package-lock.json

@@ -56,7 +56,7 @@
     "karma-verbose-reporter": "0.0.6",
     "local-web-server": "2.6.0",
     "markdown": "0.5.0",
-    "rollup": "0.68.0",
+    "rollup": "0.68.1",
     "rollup-plugin-babel": "4.1.0",
     "rollup-plugin-node-resolve": "3.4.0",
     "uglify-js": "3.4.9"