DoubleAuctin for XEE

1. XEE_DIR/experiments/doubleauction/ に設置

2. XEE_DIR/experiments/doubleauction/ で以下を実行

    npm install
   

3. XEE_DIR/config/experiment.exs に以下を追加

    experiment "DoubleAuction",
      file: "experiments/doubleauction/script.exs",
      host: "experiments/doubleauction/host.js",
      participant: "experiments/doubleauction/participant.js"