Added support for setHtml()

DriverInterface.php updated for use with MinkSelenium2Driver's new setHtml() method.
Element.php updated containing the actual setHtml() method (same location of setValue() method).

src/Behat/Mink/Driver/DriverInterface.php

@@ -313,6 +313,17 @@ public function getText($xpath);
      */
     public function getHtml($xpath);
 
+    /**
+     * Sets element's inner html by it's XPath query
+     *
+     * @param string $xpath
+     * @param string $html
+     *
+     * @throws UnsupportedDriverActionException When operation not supported by the driver
+     * @throws DriverException                  When the operation cannot be done
+     */
+    public function setHtml($xpath, $html);
+
     /**
      * Returns element's outer html by it's XPath query.
      *

src/Behat/Mink/Element/Element.php

@@ -185,6 +185,18 @@ public function getHtml()
         return $this->getSession()->getDriver()->getHtml($this->getXpath());
     }
 
+    /**
+     * Sets element innerHTML
+     *
+     * @param $html
+     *
+     * @return mixed
+     */
+    public function setHtml($html)
+    {
+        return $this->getSession()->getDriver()->setHtml($this->getXpath(), $html);
+    }
+
     /**
      * Returns element outer html.
      *