Fix namespace of cept

Hi, 

I got following error when running generated cept.

```
PHP Fatal error:  Class 'Foo\Bar\Codeception\TestGuy' not found in /path/to/testCept.php on line 3
```

**Steps to reproduce the error:**
1. <code>php codecept.phar bootstrap --namespace Foo\\Bar</code>
2. <code>php codecept.phar generate:cept functional test</code>
3. <code>php codecept.phar run functional</code>

**Similar issue:** https://github.com/Codeception/Codeception/pull/485#issuecomment-22840738
> I found that Codeception\Guy is too long name, thus I removed Codeception namespace from Guy classes.

Regards, thx