Update Vagrantfile to eliminate double ssh ports

Vagrant shares port 2222 with `vagrant up` and a custom port, even if you do not specify one.  This change resolves that.
Goes from this:
```
==> local: Forwarding ports...
    local: 22 => 2238 (adapter 1)
    local: 22 => 2222 (adapter 1)
```
to this:
```
==> local: Forwarding ports...
    local: 22 => 2238 (adapter 1)
```
Merge pull request #27 from mcheck/patch-1

Update Vagrantfile to eliminate double ssh ports