support eslint

[nevinera]

The most popular linting framework for frontend code - seems valuable to support :-)

[nevinera]

I poked at this one a bit already @JonathanWThom, but the problem I ran into is that the way you run eslint isn't consistent. Most projects seem to specify a bunch of the config for the tool by creating one or more package.json script entries that runs eslint with additional arguments supplied, and they name them just whatever they feel like.

I think we might need to hold off on this until we have a way to let users supply their own command (and/or base_command`) for certain tools through the config file, like

eslint:
  base_command: ".node_modules/bin/eslint --foo --bar --config .myconfig.json"
  filter_messages: true
  changed_files: true

I ticketed that as its own issue here just now, if you'd like to take a crack at that first :-)