Add support for proxying based on URI path

[dlee]

It would be useful if invoker proxied based on URI path as well as domain.

For example:
app.dev => app
app.dev/search => search
app.dev/chat => chat

[dlee]

The ini could look like this:

[rails]
directory = /Users/bob/rails/
domain = app
command = rails s -p $PORT

[search]
directory = /Users/bob/search/
command = searchd -p $PORT
domain = app
path_prefix = /search

[chat]
directory = /Users/bob/chat/
command = chatd -p $PORT
domain = app
path_prefix = /chat

[gnufied]

Hmm, it is def. doable. @dlee if you can open a PR I will be happy to merge. otherwise it is bit lower in my own feature list priority for next release.

[dlee]

Fixed by #123