fix typo

server.js

@@ -7,7 +7,7 @@ var path = require('path');
 var mv = require('mv');
 var fs = require('fs');
 
-var upload_dir = '/tmp/uploads';
+var upload_dir = '/tmp/uploads/';
 if (!fs.existsSync(upload_dir)){
     fs.mkdirSync(upload_dir);
 }