Added role=slider for better accessibility.

src/rzslider.js

@@ -284,6 +284,7 @@ function throttle(func, wait, options) {
         self = this;
 
       this.initElemHandles();
+      this.addAccessibility();
       this.calcViewDimensions();
       this.setMinAndMax();
 
@@ -588,6 +589,18 @@ function throttle(func, wait, options) {
       }
     },
     
+    /**
+     * Adds accessibility atributes
+     *
+     * Run only once during initialization
+     *
+     * @returns {undefined}
+     */
+    addAccessibility: function ()
+    {
+      this.sliderElem.attr("role", "slider");
+    },
+
     /**
      * Calculate dimensions that are dependent on view port size
      *