function init (debug) {
  debug.inspectOpts = {};

  var keys = Object.keys(exports.inspectOpts);
  for (var i = 0; i < keys.length; i++) {
    debug.inspectOpts[keys[i]] = exports.inspectOpts[keys[i]];
  }
}
Init logic for `debug` instances.

Create a new `inspectOpts` object in case `useColors` is set
differently for a particular `debug` instance.