chore(package): update buble to version 0.20.0

Closes #70

Author: greenkeeper[bot]

package.json

@@ -49,7 +49,7 @@
     "winston": "2.3.1"
   },
   "devDependencies": {
-    "buble": "0.15.2",
+    "buble": "0.20.0",
     "dependency-check": "2.9.1",
     "doctoc": "1.3.0",
     "eslint": "4.5.0",