chore(package): update highlight.js to version 9.1.0

http://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -9,7 +9,7 @@
   "dependencies": {
     "cheerio": "0.19.0",
     "debug": "2.2.0",
-    "highlight.js": "9.0.0",
+    "highlight.js": "9.1.0",
     "lodash": "3.10.1",
     "markdown-it": "5.0.3",
     "markdown-it-decorate": "1.2.1",