Thumbsup used to stop at the first problem processing a file.
This was a problem on large galleries where you’d need to run it again and again, fixing files as you went.
This change:
- skips problematic files and shows a summary at the end
- logs all warnings/errors to <thumbsup.log> when running the default output
Also refactor and cleanup of the logging logic.
The `debug` package reads DEBUG on first require to configure itself.
So far `log.js` is the first file to require it so it works, but if `yargs` started using `debug`
then setting `process.env.DEBUG` would do nothing here.
Instead we can use `debug.enable()` method to set the filter dynamically.
