Option to skip empty files

[jpluimers]

Right now I get an error when doing a wildcard gist upload that contains empty files. Please add an option to skip these files.

[ConradIrwin]

Hmm, ideally I'd love it if gisting empty files worked, but unfortunately the API returns an error when you try.

I'd love to see a pull request that added --skip-empty files, with an update to the documentation that if all files are empty no gist will be created.