Support unix sockets

[kanreisa]

related: #779

I've implemented it. maybe this is not breaking change.

[kornelski]

Thanks for the PR, but that is a hack.

I think it's inappropriate to use http: URL scheme for something that is not true HTTP over TCP/IP. unix is not a special, reserved hostname.

Python uses http+unix scheme for this: https://pypi.python.org/pypi/requests-unixsocket/ which seems more appropriate and avoids ambiguity.

[kanreisa]

@pornel Thanks review, I've fixed.

[kornelski]

That's better. Thanks! Can you add tests to ensure we don't break it?

[kanreisa]

@pornel yes, added 🍰

[kanreisa]

retry build please

[kornelski]

I've restarted the build

[kanreisa]

Oops, Node.js 0.10 has failed. I'll check it later.

[philpill]

Sorry, I added the comment about the failing build a bit earlier, but removed it as I'm not sure if this PR (or the work for this PR) was the cause. Thanks for looking into it.

[kornelski]

Have you checked node 0.10? If there's no simple fix for it I don't mind disabling the feature in node 0.10 (i.e. detect node 0.10 in tests and skip the tests). 0.10 is the IE6 of nodes.

[kornelski]

Since 0.10 life ends this month we can go ahead and merge this.