Fix region update

c3.js

@@ -1248,22 +1248,13 @@
             // rect for regions
             mainRegion = main.select('.regions').selectAll('rect.region')
                 .data(__regions)
-            mainRegion
-                .attr('class', classRegion)
-              .transition().duration(withTransition ? 250 : 0)
-                .attr("x", __axis_rotated ? 0 : regionStart)
-                .attr("y", __axis_rotated ? regionStart : margin.top)
-                .attr("width", __axis_rotated ? width : regionWidth)
-                .attr("height", __axis_rotated ? regionWidth : height)
             mainRegion.enter().append('rect')
+            mainRegion
                 .attr('class', classRegion)
                 .attr("x", __axis_rotated ? 0 : regionStart)
                 .attr("y", __axis_rotated ? regionStart : margin.top)
                 .attr("width", __axis_rotated ? width : regionWidth)
                 .attr("height", __axis_rotated ? regionWidth : height)
-                .attr("opacity", 0)
-              .transition().duration(withTransition ? 250 : 0)
-                .attr("opacity", 1)
             mainRegion.exit().transition().duration(withTransition ? 250 : 0)
                 .attr("opacity", 0)
                 .remove()