expand slider handle area

style/components/slider.less

@@ -11,15 +11,13 @@
 
 .@{slider-prefix-cls} {
   position: relative;
-  margin: 12px 0;
+  margin: 10px 0px 10px 7px;
-  margin-left: 7px;
+  height: 12px;
-  height: 8px;
+  border-radius: 5px;
-  width: auto;
-  border-radius: @border-radius-base;
   background-color: #e9e9e9;
   cursor: pointer;
-  border-top: 2px solid #fff;
+  border-top: 4px solid #fff;
-  border-bottom: 2px solid #fff;
+  border-bottom: 4px solid #fff;
   transition: background-color 0.3s ease;
 
   &-track {
@@ -34,6 +32,9 @@
 
   &:hover {
     background-color: #e1e1e1;
+    .@{slider-prefix-cls}-handle {
+      border-color: tint(@primary-color, 20%);
+    }
   }
 
   &:hover &-track {