Remove [DEPRECATION WARNING]: Legacy variable substitution

[ericclemmons]

[AntJanus]

From the fix:

Ref #98

Just wanted to update the library to use Ansible's latest variable substitution. Unfortunately, the wordpress/templates/vhosts will trigger the legacy error due to Apache's own variable syntax ${APACHE_LOG_DIR} which Ansible interprets as legacy code.

So, until either ansible allows per-project settings for showing deprecation warnings or until they phase the feature out completely (and thus stop giving a deprecation warning), we won't be able to get rid of it.