plack/Plack — pull request #337 by mattn (2012-10-09 04:30:11+00:00)
Title: --path argument to mount app to specified sub-directory.

I publish app via reverse proxy that opend always on my http server. So I want to start plack app without wrapper psgi script like following.

```
builder {
mount '/foo/' => Plack::Util::load_psgi 'app.psgi';
}
```

I added `--path` argument similar to work like `unicorn_rails`. How about this?
Below is a usage to do it.

```
$ plackup -p 3000 --path /foo/
```