The URI to the mongoDB is not hardcoded , config.local should contain the info to connect to the data base, for example:

To connect to a local one

 mongodb: {
              user: "",
              password: "",
              dbname: "WebArena",
              host: "localhost",
              port: 27017
            }

To connect to a remote one:

 mongodb: {
              user: "tester",
              password: "paderborn2014",
              dbname: "webarena",
              host: "ds043329.mongolab.com",
              port: 43329
            }