Update rollup to the latest version 🚀 (#130)

Author: greenkeeper[bot]

package.json

@@ -86,7 +86,7 @@
     "npm-watch": "^0.3.0",
     "nyc": "^11.1.0",
     "rimraf": "^2.6.1",
-    "rollup": "^0.51.0",
+    "rollup": "^0.52.0",
     "rollup-plugin-buble": "^0.18.0",
     "uglify-js": "^3.0.28",
     "vue": "^2.4.2",