STDIO support for csonc CLI utility

`csonc` has very limited usefulness due to the lack of supporting STDIN and STDOUT.

A use case I have is:

`csonc < pixie.cson | underscore pluck name | ...`

Currently that would involve some tempfile hacks to accomplish.

Using STDIO would allow `csonc` to be used in a much broader range of applications and to be a good command line citizen.

I'm currently stuck on updating the tests for the cli, but I can update them if there is interest in this patch.