code: function readDb(cb) {
                fs.exists(t.getDbFilename(), function(exists) {
                  if (exists) {
                    fs.readFile(t.getDbFilename(), {encoding: "utf-8"}, cb); 
                  } else {
                    cb(null, null); 
                  }
                });
              }
docs: Reads the db.json, if it exists
  
  @param cb