title: Can not start special firefox with Json configuration on Selenium 3
body: <p>i using Selenium Grid and configuring the node and hub by Json
  here is my json </p>
  
  <pre><code>{
    "capabilities":
    [
      {
        "browserName": "firefox",
        "browser-version": "38.8.0",
        "maxInstances": 5,
        "firefox_binary": "C:/Program Files (x86)/secutix/Matterhorn_V3/FireFoxPortableESR/App/Firefox/firefox.exe",
        "seleniumProtocol": "WebDriver"
      },
      {
        "browserName": "chrome",
        "maxInstances": 5,
        "seleniumProtocol": "WebDriver"
      },
      {
        "browserName": "internet explorer",
        "maxInstances": 1,
        "seleniumProtocol": "WebDriver"
      }
    ],
    "proxy": "org.openqa.grid.selenium.proxy.DefaultRemoteProxy",
    "maxSession": 5,
    "port": 5568,
    "register": true,
    "registerCycle": 5000,
    "hub": "http://localhost:4444",
    "nodeStatusCheckTimeout": 5000,
    "nodePolling": 5000,
    "role": "node",
    "unregisterIfStillDownAfter": 60000,
    "downPollingLimit": 2,
    "debug": false,
    "servlets" : [],
    "withoutServlets": [],
    "custom": {}
  }
  </code></pre>
  
  <p><br/>I started Hub (fine)
  <br/>I started Node (fine)
  <br/> But when i run serenity test by maven cmd "mvn clean verify"
  there are only Current Firefox ver 45.6 was created. The FireFoxPortableESR is none. <br/>
  <em>In case, change Selenium-server-standalon from 3.0 to 2.53, it working okay.</em> 
  <br/><strong>so how to call FireFoxPortableESR when use Selenium 3.0*</strong>  </p>