Add way to fetch the unparsed command string from a session.

[andrewchambers]

No description provided.

[progrium]

As reasonable as this is, what do other people think about this? You can basically get this by rejoining the split command string. I'm curious, @andrewchambers what is the use case for this? I suspected the common case would be like you're using os.Args and nobody has requested something like this until now.

[andrewchambers]

I am forwarding to another ssh server, and letting it handle the command exactly as it was sent (things like) FOO=bar command

I didn't trust shlex+join to preserve all bash semantics, even though perhaps it might, I couldn't guarantee it, so did this to ensure it works in every case.

[belak]

At my old job I would have been looking for this as well - there was some custom parsing we wanted to do with the commands that wasn't possible when it came through shlex

[belak]

This was merged as a part of #110. Thanks for submitting this!