Making opts.cwd persist through chained calls

[brynbellomy]

Basically what the title says. I really didn't want to barf all over your implementation, which is really elegant and concise, so I took as much care as I could in not adding unnecessary fields to objects, not repeating anything, etc. However, I did have to make a second call to normalizeArguments(), but to balance that out, I modified procSteam() so that the first argument could be an object containing the already-normalized argument fields. In this case, the call to normalizeArguments() is not made inside of procStreams() -- no code is actually run twice. It was the best workaround I could think of without doing some fundamental rewriting.

Let me know if you have a better idea about how to implement this -- I'm all ears.

[polotek]

Hey it look like this is failing travis tests. I haven't had a chance to look over it yet. But can you look into that?

[popomore]

It seems travis's problem.

https://travis-ci.org/polotek/procstreams/jobs/2761505