Sanitize the generated hostname
Sanitize the generated hostname

Since we take the role name provided by `molecule init`, and pass that
to Vagrant, we can generate invalid hosnames[1].  I am going to assume
roles are generally named in such a way that they are valid Vagrant
hostnames[1].  However, roles tend to use underscore and dashes
interchangeably.  Also, when using roles from galaxy they contain
`namespace.rolename`.  Linux will treat these hostnames PS1 as
`namespace` which is just lame.

[1] The hostname set for the VM should only contain letters, numbers,
    hyphens or dots. It cannot start with a hyphen or dot.

metacloud/molecule,cimarron-pistoncloud/molecule,retr0h/molecule,rjfellman/molecule,j0lly/molecule,j0lly/molecule,rgreinho/molecule,retr0h/maquina,j0lly/molecule,rgreinho/molecule,kharkevich/molecule,rjfellman/molecule,rjfellman/molecule,metacloud/molecule,kireledan/molecule,cimarron-pistoncloud/molecule,metacloud/molecule,cimarron-pistoncloud/molecule,rgreinho/molecule