Merge pull request #766 from esteinborn/patch-1

DOCS: Set vagrant_box to ubuntu1404 for PHP 5.6

Author: geerlingguy

docs/other/php-56.md

@@ -11,6 +11,7 @@ Ubuntu 16.04 Xenial defaults to PHP 7.0 in it's system packages. No older versio
 Ondřej Surý's PPA for PHP 7.0 is used to install PHP 7, but you can switch to using different 5.6 packages instead by making the following changes to `config.yml`:
 
 ```yaml
+vagrant_box: geerlingguy/ubuntu1404
 php_version: "5.6"
 php_packages:
   - php5