Update colorbox 1.6.4

sigal/themes/colorbox/static/css/colorbox.css

@@ -2,7 +2,7 @@
     Colorbox Core Style:
     The following CSS is consistent between example themes and should not be altered.
 */
-#colorbox, #cboxOverlay, #cboxWrapper{position:absolute; top:0; left:0; z-index:9999; overflow:hidden;}
+#colorbox, #cboxOverlay, #cboxWrapper{position:absolute; top:0; left:0; z-index:9999; overflow:hidden; -webkit-transform: translate3d(0,0,0);}
 #cboxWrapper {max-width:none;}
 #cboxOverlay{position:fixed; width:100%; height:100%;}
 #cboxMiddleLeft, #cboxBottomLeft{clear:left;}