chore(package): update rollup-plugin-uglify to version 4.0.0

Closes #32

Author: greenkeeper[bot]

package.json

@@ -32,7 +32,7 @@
     "rollup-plugin-commonjs": "8.2.6",
     "rollup-plugin-node-resolve": "3.0.0",
     "rollup-plugin-sourcemaps": "^0.4.1",
-    "rollup-plugin-uglify": "^2.0.1",
+    "rollup-plugin-uglify": "^4.0.0",
     "sinon": "4.1.3"
   },
   "keywords": [