Prevent apache exiting after failing to find a webroot.

An `exit 1` from the apache script aborts the entire provision, this isn't ideal.

Instead we now simply link the webroot if we find it, otherwise it remains

fixes #29
What if you don't want a symlinked dir?

Also, I find when provisioning a brand new box when I want to go in and do `composer create-project` then provisioning doesn't complete.

Instead I have to add a www folder (pretty much arbitarily) just to get my machine provisioned