title: Equivalent of FirefoxDriver(*profile*) for MarionetteDriver in Selenium Webdriver?
body: <p>I'm trying to convert some Selenium tests from <code>FirefoxDriver</code> to <code>MarionetteDriver</code>, but I'm hitting issues regarding PKI. My solution up to now has been to use various Firefox profiles which only have one custom PKI and automatically choose that for login purposes. However, it seems that the <code>MarionetteDriver</code> constructor doesn't have the capability to launch Firefox with a custom profile. How do I fix this?</p>
  
  <p>I got around this in Python by having Python start Firefox before connecting to it with Marionette, but I don't know if Selenium WebDriver has this capability.</p>