Fix issue w/vagrant's ssh port forwarding

[defvol]

Fixes #3

[defvol]

As @stuporglue pointed out in #3, the way to fix it is by adding id: 'ssh' to the port override config.

See also:
hashicorp/vagrant#3232 (comment)

[defvol]

Actually #4 fixes this

Warnings:
* `config.vm.customize` calls are VirtualBox-specific. If you're
using any other provider, you'll have to use config.vm.provider in a
v2 configuration block.
* Unknown network type 'forwarded_port' will be ignored.