Support for stdin processing

[pke]

I have an in memory byte array that I would like to process with exiftool.
The tool itself supports reading from stdin however node-exiftool seems to only accept disk files.

Is this a trivial change or would need more work? Happy to provide a PR.

[dminkovsky]

Whoops I just opened a dupe #53.

I'm not great with Unix pipes via Node, but https://github.com/nathanpeck/exiftool seems to provide an example.

[pke]

Where exactly does it provide the example?

[aiavci]

Is there an update on this issue by any chance? Perhaps an example or fix?