Fix copy temporary folder

This is needed to copy just the contents of temporary folder, instead of the folder itself.
Ciao @omissis, mainly because without this diff, i have this situation after the setup.sh execution:

```
./setup.sh

==========================
Drupal Ignite Setup Script
==========================

This script will guide you into setting up your Drupal Ignite installation.

Please enter Site's Name:
example.com

Please enter Site's Root Folder:
/tmp/example-com

Please enter Site's Domain:
example-com

Folder /tmp/example-com doesn't exist, should I create it now? [y/n]
y

#!/usr/bin/env php
All settings correct for using Composer
The defined install dir (bin) does not exist.
Could not open input file: bin/composer.phar
/tmp/drupal-ignite-twinbit

Done.

$ ls -al /tmp/example-com
total 0
drwxr-xr-x   3 paolomainardi  wheel  102 Sep 22 13:35 .
drwxrwxrwt  21 root           wheel  714 Sep 22 13:35 ..
drwxr-xr-x  18 paolomainardi  wheel  612 Sep 22 13:35 drupal-ignite-core-a72d7bda371a9d5168d0ade88cbd6104
```