remote: add process.{stdout,stderr}

First I refactored the actor protocol to take stdio data as argument and not member of an object (like `{stream:'stdout',val:"foo"}`) so it works with buffers too.

Then i added `process.{stdout,stderr}` as through streams for remote scripts.

- [ ] Should I swap `require('stream').Transform` with `require('readable-stream').Transform`, for `0.8.x` support?
- [ ] <del>Should the remote fn actually override `process.{stdout,stderr}` instead of just using the passed in `process`, so node modules like `clear`, which are not in the same scope, also get to use the patched stdio streams?</del>