Remove highlight.js

package.json

@@ -31,7 +31,6 @@
     "express": "^4.14.0",
     "express-session": "^1.14.1",
     "gravatar": "^1.5.2",
-    "highlight.js": "^9.6.0",
     "md5": "^2.2.1",
     "moemark-renderer": "^1.2.0",
     "moment": "^2.15.0",

utility.js

@@ -29,7 +29,6 @@ let moment = require('moment');
 let url = require('url');
 let querystring = require('querystring');
 let pygmentize = require('pygmentize-bundled-cached');
-let highlightjs = require('highlight.js');
 let gravatar = require('gravatar');
 let AdmZip = require('adm-zip');