chore(package): update rollup-plugin-commonjs to version 9.1.8

Closes #13

Author: greenkeeper[bot]

package.json

@@ -107,7 +107,7 @@
     "replace-in-file": "^3.0.0-beta.2",
     "rimraf": "^2.6.1",
     "rollup": "^0.55.0",
-    "rollup-plugin-commonjs": "^8.0.2",
+    "rollup-plugin-commonjs": "^9.1.8",
     "rollup-plugin-copy": "^0.2.3",
     "rollup-plugin-node-resolve": "^3.0.0",
     "rollup-plugin-sourcemaps": "^0.4.2",