adding the different PHP versions to the docs in addition to general
updates

adding `phpnginx` or `php55nginx` will pull PHP 5.5 while `php56nginx`
will pull PHP 5.6

to avoid any errors while experimenting on the master branch

Update README.md (a typo)

Develop

* 'develop' of https://github.com/LaraDock/starter:
  add app url to the config and set it to laravel.dev

add the Docker-Machine mapping step

add a commented out `extra_hosts` to be uncommented incase of the usage
of `docker-machine` for mapping the `laravel.dev` url to the VM IP
inside the VM container.

Add minimum required version of Docker-Compose