Confusing wording in the README regarding docroot

Maybe I was just being dumb, but I got really confused by the wording in the [Apache Virtual Hosts](https://github.com/r8/vagrant-lamp#apache-virtual-hosts) section of the readme. I thought it was implying that it would actually create an empty directory for me in `public/` after I created a `.json` file.

I spent a fair amount of time trying to debug why the directory was not being created for me.