Update dependency rollup-plugin-commonjs to v9.1.4 (#21)

Author: renovate[bot]

package-lock.json

@@ -37,7 +37,7 @@
     "prettier": "1.14.0",
     "rimraf": "2.6.2",
     "rollup": "0.63.4",
-    "rollup-plugin-commonjs": "9.1.3",
+    "rollup-plugin-commonjs": "9.1.4",
     "rollup-plugin-node-builtins": "2.1.2",
     "tslint": "5.10.0",
     "typescript": "2.9.2"