Fix TypeError in sliders.js with non webkit browsers.

dist/js/ratchet.js

@@ -716,9 +716,11 @@
   };
 
   var getScroll = function () {
+    if ('webkitTransform' in slider.style) {
       var translate3d = slider.style.webkitTransform.match(/translate3d\(([^,]*)/);
       var ret = translate3d ? translate3d[1] : 0;
       return parseInt(ret, 10);
+    }
   };
 
   var setSlideNumber = function (offset) {

docs/dist/js/ratchet.js

@@ -716,9 +716,11 @@
   };
 
   var getScroll = function () {
+    if ('webkitTransform' in slider.style) {
       var translate3d = slider.style.webkitTransform.match(/translate3d\(([^,]*)/);
       var ret = translate3d ? translate3d[1] : 0;
       return parseInt(ret, 10);
+    }
   };
 
   var setSlideNumber = function (offset) {

js/sliders.js

@@ -36,9 +36,11 @@
   };
 
   var getScroll = function () {
+    if ('webkitTransform' in slider.style) {
       var translate3d = slider.style.webkitTransform.match(/translate3d\(([^,]*)/);
       var ret = translate3d ? translate3d[1] : 0;
       return parseInt(ret, 10);
+    }
   };
 
   var setSlideNumber = function (offset) {