code: function destroy(req, res, next) {
    db.tags.del(req.params.tag, function(err) {
      if(err) { return next(err); }
      res.json(null);
      signals.emit('tag:destroy', req.params.tag);
    });
  }
docs: URL: /tags/:tag
  
  Method: DELETE
  
  Events:
  
  * `tag:destroy`
  
  Status codes:
  
  * `200` ok
  * `404` not found