Removed react-draggable2 style import - Fixes mui#218

Author: Hai Nguyen

src/less/components/slider.less

@@ -1,4 +1,6 @@
-@import (inline) "../../../node_modules/react-draggable2/lib/styles.css";
+.react-draggable-dragging {
+  user-select: none;
+}
 
 .mui-slider {
   @fill-gutter: @slider-handle-size-disabled - @slider-track-size;