title: Extent Report getting overwritten instead of getting appended for multiple tests
body: <p>I am using <code>Extent Report Version 4.0.9</code> to generate report for two of my tests. I am working on selenium, java, testng, cucumber, maven project. I have two TestRunner files in my cucumberOptions which I run one after the other using <code>POM.xml</code>. 
  When I run only one TestRunner, the Extent Report gets generated as expected. But when I run both TestRunners one after the other, the Extent Report which is generated by the second test overwrites the one generated by the first one.
  How do I append the ExtentReport generated by the second test to that generated by the first test?</p>
  
  <p>Here is my ExtentReporterListener code:</p>
  
  <pre><code>public class ExtentReporterListener {
  
      private static Logger log = LogManager.getLogger(ExceptionHandler.class);
      private static final String TEST_OUTPUT = TestConfiguration.USER_DIR + "\\test-output\\Screenshots";
  
      public static ExtentHtmlReporter report = null;
      public static ExtentReports extent = null;
      public static ExtentTest feature = null;
      public static ExtentTest scenario = null;
  
      public static ExtentReports setUp() {
          String reportLocation = "./Reports/Extent_Report.html";
  
          report = new ExtentHtmlReporter(reportLocation);
          report.config().setDocumentTitle("Word press Automation Test Report");
          report.config().setReportName("Word Press Automation Test Report");
          report.config().setTheme(Theme.STANDARD);
          log.info("Extent Report location initialized...");
          report.start();
  
          extent = new ExtentReports();
          extent.attachReporter(report);
          extent.setSystemInfo("Application", "Word Press");
  
          return extent;
      }
  }
  
  This is my testng.xml:
  
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd"&gt;
  &lt;suite name="Suite"&gt;
    &lt;listeners&gt;
      &lt;listener class-name = "listener-class" /&gt;
    &lt;/listeners&gt;
    &lt;test thread-count="5" name="frontEnd"&gt;
    &lt;parameter name="URL" value="front-end-url" /&gt;
      &lt;classes&gt;
        &lt;class name="frontendTestRunner"/&gt;
      &lt;/classes&gt;
    &lt;/test&gt;
    &lt;test thread-count="5" name="Backend"&gt;
    &lt;parameter name="URL" value="back-end-url" /&gt; 
      &lt;classes&gt;
        &lt;class name="backendtestrunner"/&gt;
      &lt;/classes&gt;
    &lt;/test&gt;  &lt;!-- Test --&gt;
  &lt;/suite&gt; &lt;!-- Suite --&gt;
  
  </code></pre>
  
  <p>I am using Extent Report version 4. Somehow <code>setAppendExisting(true);</code> method which was in older version doesnot seem to exist in version 4.</p>