Updated the Vagrantfile to install vagrant-hostsupdater if missing, and to include version requirements for Vagrant (>=2.1) and VirtualBox (>=5.2).
Updated the Vagrantfile to install vagrant-hostsupdater if missing, and to include version requirements for Vagrant (>=2.1) and VirtualBox (>=5.2).

wplib/wplib-box,wplib/wplib-box,wplib/wplib-box