Feature: I want to be able to specify the location of the interfaces file.

It would be cool to be able to not have to edit the global /etc/network/interfaces file...  While it does provide compatibility with something like ifscheme, it's not really super great thing I think.

Something like:

```sh
$ wifi --file ~/.interfaces connect home
```

It would also allow us to have "profiles".

I also want there to be a .wifirc file.  It would allow user to specify defaults for --interface and --file.