Implement visible rail feature.

Now the scrollbars are wrapped by rail elements, and
the styles and scripts are heavily changed to implement the feature.

src/perfect-scrollbar.css

@@ -1,75 +1,111 @@
-.ps-container .ps-scrollbar-x {
+.ps-container .ps-scrollbar-x-rail {
     position: absolute; /* please don't change 'position' */
-    bottom: 3px; /* there must be 'bottom' for ps-scrollbar-x */
+    bottom: 3px; /* there must be 'bottom' for ps-scrollbar-x-rail */
     height: 8px;
-    background-color: #aaa;
     -webkit-border-radius: 4px;
     -moz-border-radius: 4px;
     border-radius: 4px;
     opacity: 0;
     filter: alpha(opacity = 0);
-    -o-transition: opacity .2s linear;
-    -webkit-transition: opacity.2s linear;
-    -moz-transition: opacity .2s linear;
-    transition: opacity .2s linear;
+    -o-transition: background-color .2s linear, opacity .2s linear;
+    -webkit-transition: background-color.2s linear, opacity .2s linear;
+    -moz-transition: background-color .2s linear, opacity .2s linear;
+    transition: background-color .2s linear, opacity .2s linear;
+}
+
+.ps-container:hover .ps-scrollbar-x-rail,
+.ps-container.hover .ps-scrollbar-x-rail {
+    opacity: 0.6;
+    filter: alpha(opacity = 60);
+}
+
+.ps-container .ps-scrollbar-x-rail:hover,
+.ps-container .ps-scrollbar-x-rail.hover {
+    background-color: #eee;
+    opacity: 0.9;
+    filter: alpha(opacity = 90);
+}
+
+.ps-container .ps-scrollbar-x-rail.in-scrolling {
+    opacity: 0.9;
+    filter: alpha(opacity = 90);
+}
+
+.ps-container .ps-scrollbar-y-rail {
+    position: absolute; /* please don't change 'position' */
+    right: 3px; /* there must be 'right' for ps-scrollbar-y-rail */
+    width: 8px;
+    -webkit-border-radius: 4px;
+    -moz-border-radius: 4px;
+    border-radius: 4px;
+    opacity: 0;
+    filter: alpha(opacity = 0);
+    -o-transition: background-color .2s linear, opacity .2s linear;
+    -webkit-transition: background-color.2s linear, opacity .2s linear;
+    -moz-transition: background-color .2s linear, opacity .2s linear;
+    transition: background-color .2s linear, opacity .2s linear;
+}
+
+.ps-container:hover .ps-scrollbar-y-rail,
+.ps-container.hover .ps-scrollbar-y-rail {
+    opacity: 0.6;
+    filter: alpha(opacity = 60);
+}
+
+.ps-container .ps-scrollbar-y-rail:hover,
+.ps-container .ps-scrollbar-y-rail.hover {
+    background-color: #eee;
+    opacity: 0.9;
+    filter: alpha(opacity = 90);
+}
+
+.ps-container .ps-scrollbar-y-rail.in-scrolling {
+    opacity: 0.9;
+    filter: alpha(opacity = 90);
+}
+
+.ps-container .ps-scrollbar-x {
+    position: absolute; /* please don't change 'position' */
+    bottom: 0; /* there must be 'bottom' for ps-scrollbar-x */
+    height: 8px;
+    background-color: #aaa;
+    -webkit-border-radius: 4px;
+    -moz-border-radius: 4px;
+    border-radius: 4px;
+    -o-transition: background-color .2s linear;
+    -webkit-transition: background-color.2s linear;
+    -moz-transition: background-color .2s linear;
+    transition: background-color .2s linear;
 }
 
 .ps-container.ie6 .ps-scrollbar-x {
     font-size: 0; /* fixed scrollbar height in xp sp3 ie6 */
 }
 
-.ps-container:hover .ps-scrollbar-x,
-.ps-container.hover .ps-scrollbar-x {
-    opacity: 0.6;
-    filter: alpha(opacity = 60);
-}
-
-.ps-container .ps-scrollbar-x:hover,
-.ps-container .ps-scrollbar-x.hover {
-    opacity: 0.9;
-    filter: alpha(opacity = 90);
-    cursor:default;
-}
-
-.ps-container .ps-scrollbar-x.in-scrolling {
-    opacity: 0.9;
-    filter: alpha(opacity = 90);
+.ps-container .ps-scrollbar-x-rail:hover .ps-scrollbar-x,
+.ps-container .ps-scrollbar-x-rail.hover .ps-scrollbar-x {
+    background-color: #999;
 }
 
 .ps-container .ps-scrollbar-y {
     position: absolute; /* please don't change 'position' */
-    right: 3px; /* there must be 'right' for ps-scrollbar-y */
+    right: 0; /* there must be 'right' for ps-scrollbar-y */
     width: 8px;
     background-color: #aaa;
     -webkit-border-radius: 4px;
     -moz-border-radius: 4px;
     border-radius: 4px;
-    opacity: 0;
-    filter: alpha(opacity = 0);
-    -o-transition: opacity .2s linear;
-    -webkit-transition: opacity.2s linear;
-    -moz-transition: opacity .2s linear;
-    transition: opacity .2s linear;
+    -o-transition: background-color .2s linear;
+    -webkit-transition: background-color.2s linear;
+    -moz-transition: background-color .2s linear;
+    transition: background-color .2s linear;
 }
 
 .ps-container.ie .ps-scrollbar-y {
     font-size: 0; /* fixed scrollbar height in xp sp3 ie6 */
 }
 
-.ps-container:hover .ps-scrollbar-y,
-.ps-container.hover .ps-scrollbar-y {
-    opacity: 0.6;
-    filter: alpha(opacity = 60);
-}
-
-.ps-container .ps-scrollbar-y:hover,
-.ps-container .ps-scrollbar-y.hover {
-    opacity: 0.9;
-    filter: alpha(opacity = 90);
-    cursor: default;
-}
-
-.ps-container .ps-scrollbar-y.in-scrolling {
-    opacity: 0.9;
-    filter: alpha(opacity = 90);
+.ps-container .ps-scrollbar-y-rail:hover .ps-scrollbar-y,
+.ps-container .ps-scrollbar-y-rail.hover .ps-scrollbar-y {
+    background-color: #999;
 }