Fixes for travis

.travis.yml

@@ -1,9 +1,7 @@
 language: node_js
 node_js:
-  - "9"
   - "8"
-  - "7"
-  - "6"
+  - "10"
 env:
   - CXX=g++-4.8
 cache:

src/controllers/server.js

@@ -33,7 +33,6 @@ const extendify = require('extendify');
 const Ansi = require('ansi-escape-sequences');
 const Request = require('request');
 const Cache = require('memory-cache');
-const Randomstring = require('randomstring');
 
 const Log = require('./../helpers/logger');
 const Docker = require('./docker');