Feature/zlib (Closes #96) DON'T MERGE YET

This works in practice but I was unable to make it work without writing the `bundle.tar.gz` to disk. Previously we got a readable stream from `bundle.zip` and handed it to [request](https://github.com/mikeal/request)'s [form-data](https://github.com/felixge/node-form-data) object:

https://github.com/Versal/sdk/blob/master/src/upload.coffee#L97

Since piping to `zlib.createGzip()` creates a readable stream also I figured that it could also be handed to `form().append` also but no dice. I fiddled with everything under the sun to no avail (including working with form-data directly and trying to convert the stream to an array with [stream-to-array](https://www.npmjs.org/package/stream-to-array))