document that link.line.(width|color) is not supported with circularity

Author: antoinerg

src/traces/sankey/attributes.js

@@ -177,7 +177,8 @@ var attrs = module.exports = overrideAll({
                 dflt: colorAttrs.defaultLine,
                 arrayOk: true,
                 description: [
-                    'Sets the color of the `line` around each `link`.'
+                    'Sets the color of the `line` around each `link`.',
+                    'Note that in the presence of circular links this attribute is ignored.'
                 ].join(' ')
             },
             width: {
@@ -187,7 +188,8 @@ var attrs = module.exports = overrideAll({
                 dflt: 0,
                 arrayOk: true,
                 description: [
-                    'Sets the width (in px) of the `line` around each `link`.'
+                    'Sets the width (in px) of the `line` around each `link`.',
+                    'Note that in the presence of circular links this attribute is ignored.'
                 ].join(' ')
             }
         },

src/traces/sankey/render.js

@@ -128,7 +128,7 @@ function linkPath() {
     var curvature = 0.5;
     function path(d) {
         if(d.circular) {
-            return d.link.path;
+            return d.link.path; // TODO: turn this into a closed path to support link.line.(width|color)
         } else {
             var x0 = d.link.source.x1;
             var x1 = d.link.target.x0;