Update ReadMe for using Xvfb with "--headless"

Author: mdmintz

README.md

@@ -265,7 +265,9 @@ If you're planning on using the full power of this test framework, there are a f
 
 * Setup your Selenium Grid and update your *.cfg file to point there. An example config file called selenium_server_config_example.cfg has been provided for you in the grid folder. The start-selenium-node.bat and start-selenium-server.sh files are for running your grid. In an example situation, your Selenium Grid server might live on a unix box and your Selenium Grid nodes might live on EC2 Windows virtual machines. When your build server runs a Selenium test, it would connect to your Selenium Grid to find out which Grid browser nodes are available to run that test. To simplify things, you can use [Browser Stack](https://www.browserstack.com/automate) as your entire Selenium Grid (and let them do all the fun work of maintaining the grid for you).
 
-* There are ways of running your tests from Jenkins without having to utilize a remote machine. One way is by using PhantomJS as your browser (it runs headlessly). Another way is by using Xvfb (another headless system). [There's a plugin for Xvfb in Jenkins](https://wiki.jenkins-ci.org/display/JENKINS/Xvfb+Plugin). Here are some more helpful resources I found regarding the use of Xvfb:
+* There are ways of running your tests from Jenkins without having to utilize a remote machine. One way is by using PhantomJS as your browser (it runs headlessly). Another way is by using Xvfb (another headless system). [There's a plugin for Xvfb in Jenkins](https://wiki.jenkins-ci.org/display/JENKINS/Xvfb+Plugin).
+If you have Xvfb running in the background, you can add ``--headless`` to your run command in order to utilize it.
+Here are some more helpful resources I found regarding the use of Xvfb:
 1. http://stackoverflow.com/questions/6183276/how-do-i-run-selenium-in-xvfb
 2. http://qxf2.com/blog/xvfb-plugin-for-jenkins-selenium/
 3. http://stackoverflow.com/questions/27202131/firefox-started-by-selenium-ignores-the-display-created-by-pyvirtualdisplay