Streaming support

[kellyjonbrazil]

Enhancement to add streaming support so the entire JSON document doesn't need to be loaded to start processing.

Looks like the ijson library might handle a lot of this. I think I might be able to create a jello -S (for streaming) option that uses the ijson library to parse STDIN and return _ as a generator/iterator of JSON objects - whether it's an array or a top-level of JSON objects.