chore(package): update rollup-plugin-filesize to version 6.0.1

Closes #41

Author: greenkeeper[bot]

package.json

@@ -86,7 +86,7 @@
     "rimraf": "2.5.4",
     "rollup": "0.36.4",
     "rollup-plugin-babel": "2.6.1",
-    "rollup-plugin-filesize": "1.0.1",
+    "rollup-plugin-filesize": "6.0.1",
     "rollup-watch": "2.5.0",
     "semver": "5.3.0",
     "sinon": "1.17.6",