Add axis label format option

c3.js

@@ -72,6 +72,7 @@
             __axis_y_text = getConfig(['axis','y','text'], null),
             __axis_y_rescale = getConfig(['axis','y','rescale'], true),
             __axis_y_inner = getConfig(['axis','y','inner'], false),
+            __axis_y_format = getConfig(['axis','y','format'], function(d){ return d; }),
             __axis_y2_show = getConfig(['axis','y2','show'], false),
             __axis_y2_max = getConfig(['axis','y2','max'], null),
             __axis_y2_min = getConfig(['axis','y2','min'], null),
@@ -79,6 +80,7 @@
             __axis_y2_text = getConfig(['axis','y2','text'], null),
             __axis_y2_rescale = getConfig(['axis','y2','rescale'], true),
             __axis_y2_inner = getConfig(['axis','y2','inner'], false),
+            __axis_y2_format = getConfig(['axis','y2','format'], function(d){ return d; }),
             __axis_rotated = getConfig(['axis','rotated'], false);
 
         // grid
@@ -833,6 +835,8 @@
             subY2.domain(y2.domain());
 
             xAxis.ticks(data.length < 10 ? data.length : 10);
+            yAxis.ticks(3).outerTickSize(0).tickFormat(__axis_y_format);
+            yAxis2.ticks(3).outerTickSize(0).tickFormat(__axis_y2_format);
 
             /*-- Main Region --*/