bring back sharp axes/grids (fix #204)

c3.js

@@ -336,13 +336,14 @@
             subXOrient = __axis_rotated ? "left" : "bottom";
 
         var translate = {
-            main : function () { return "translate(" + margin.left + "," + margin.top + ")"; },
+
-            context : function () { return "translate(" + margin2.left + "," + margin2.top + ")"; },
+			main : function () { return "translate(" + (Math.ceil(margin.left) + 0.5) + "," + (Math.ceil(margin.top) + 0.5) + ")"; },
+			context : function () { return "translate(" + (Math.ceil(margin2.left) + 0.5) + "," + (Math.ceil(margin2.top) + 0.5) + ")"; },
             legend : function () { return "translate(" + margin3.left + "," + margin3.top + ")"; },
             x : function () { return "translate(0," + (__axis_rotated ? 0 : height) + ")"; },
             y : function () { return "translate(0," + (__axis_rotated ? height : 0) + ")"; },
             y2 : function () { return "translate(" + (__axis_rotated ? 0 : width) + "," + (__axis_rotated ? 1 : 0) + ")"; },
-            subx : function () { return "translate(0," + (__axis_rotated ? 0 : height2) + ")"; },
+			subx : function () { return "translate(0," + (__axis_rotated ? 0 : Math.ceil(height2)) + ")"; },
             arc: function () { return "translate(" + width / 2 + "," + height / 2 + ")"; }
         };