Add small margin to grid clippath

src/core.js

@@ -930,9 +930,13 @@ c3_chart_internal_fn.updateSvgSize = function () {
     var $$ = this,
         brush = $$.svg.select(".c3-brush .background");
     $$.svg.attr('width', $$.currentWidth + (isNode() ? 10 : 0)).attr('height', $$.currentHeight); 
-    $$.svg.selectAll(['#' + $$.clipId, '#' + $$.clipIdForGrid]).select('rect')
+    $$.svg.selectAll('#' + $$.clipId).select('rect')
         .attr('width', $$.width)
         .attr('height', $$.height);
+    // Additional 1px margin not to make last grid line transparent
+    $$.svg.selectAll('#' + $$.clipIdForGrid).select('rect')
+        .attr('width', $$.width+1)
+        .attr('height', $$.height+1);
     $$.svg.select('#' + $$.clipIdForXAxis).select('rect')
         .attr('x', $$.getXAxisClipX.bind($$))
         .attr('y', $$.getXAxisClipY.bind($$))