Json schema for config files

There are editors and command line validation tools that support json schema for nice auto-complete and validation of json files. It's often useful to provide a json schema when your utility takes a json file as input, as HTMLHint does with the .htmlhintrc json configuration files. I made a schema file for the .htmlhintrc file which includes HTMLHint specific options. It sets "additionalProperties" to true to allow jshint and csshint options, but doesn't include schema for them.