upgrade slider

package.json

@@ -50,7 +50,7 @@
     "rc-progress": "~1.0.0",
     "rc-radio": "~2.0.0",
     "rc-select": "~4.5.2",
-    "rc-slider": "~1.3.1",
+    "rc-slider": "~1.4.0",
     "rc-steps": "~1.1.4",
     "rc-switch": "~1.2.0",
     "rc-table": "~3.1.0",

style/components/slider.less

@@ -133,7 +133,7 @@
       display: none;
     }
 
-    &-placement-top { 
+    &-placement-points-bc-tc { 
       padding: @slider-tooltip-arrow-width 0 @slider-tooltip-distance 0;
     }
 
@@ -158,7 +158,7 @@
       border-style: solid;
     }
 
-    &-placement-top &-arrow {
+    &-placement-points-bc-tc &-arrow {
       bottom: @slider-tooltip-distance - @slider-tooltip-arrow-width;
       left: 50%;
       margin-left: -@slider-tooltip-arrow-width;