#587 Graph labeling issue

Large graph labels could cause wrapping inside the tick tags adding to determine maximum size, adding to svg element instead of html fixes this issue.

src/axis.js

@@ -255,7 +255,7 @@ c3_chart_internal_fn.getMaxTickWidth = function (id) {
             scale = $$.x.copy().domain($$.getXDomain(targetsToShow));
             axis = $$.getXAxis(scale, $$.xOrient, $$.getXAxisTickFormat(), config.axis_x_tick_values ? config.axis_x_tick_values : $$.xAxis.tickValues());
         }
-        $$.d3.select('body').append("g").style('visibility', 'hidden').call(axis).each(function () {
+        $$.svg.append("g").style('visibility', 'hidden').call(axis).each(function () {
             $$.d3.select(this).selectAll('text').each(function () {
                 var box = this.getBoundingClientRect();
                 if (maxWidth < box.width) { maxWidth = box.width; }