chore(package): update rollup to version 0.56.2 (#1627)

Author: greenkeeper[bot]

package.json

@@ -42,7 +42,7 @@
     "local-web-server": "2.4.0",
     "markdown": "^0.5.0",
     "pdfjs-dist": "2.0.385",
-    "rollup": "0.56.1",
+    "rollup": "0.56.2",
     "rollup-plugin-babel": "3.0.3",
     "uglify-js": "3.3.11"
   },