Fixed 'undefined method join for String' bug

Fixed 'undefined method join for String' bug, `String` object do not have a join method.

Testing environment:
* OS: ubuntu
* OS release: 14.04
* Ruby version: ruby 1.8.7 (2014-01-28 patchlevel 376) [x86_64-linux]

How to reproduce the bug:
```bash
git clone https://github.com/urbanadventurer/WhatWeb
cd WhatWeb
make install
whatweb "https://example.com"
```