Add Element.matches which has all modern browser support

Author: er1c

src/main/scala/org/scalajs/dom/raw/lib.scala

@@ -817,6 +817,13 @@ abstract class Element
    */
   def insertAdjacentHTML(where: String, html: String): Unit = js.native
 
+  /**
+   * Supported by FF>34, Opera>21, Chrome>34, IE>9, Safari>4
+   *
+   * @see https://developer.mozilla.org/en-US/docs/Web/API/Element/matches
+   */
+  def matches(selector: String): Boolean = js.native
+
   /**
    * getAttribute() returns the value of the named attribute on the specified element.
    * If the named attribute does not exist, the value returned will either be null or ""