switched contextOpacity from 0.255 to 0..1

(cherry picked from commit def1b11)

Author: monfera

src/traces/parcoords/attributes.js

@@ -165,11 +165,11 @@ module.exports = {
 
         contextopacity: {
             valType: 'number',
-            dflt: 16,
+            dflt: 0.025,
             min: 0,
-            max: 255,
+            max: 1,
             role: 'style',
-            description: 'Opacity of the context lines, on a scale of 0 (invisible) to 255 (fully opaque).'
+            description: 'Opacity of the context lines, on a scale of 0 (invisible) to 1 (fully opaque).'
         },
 
         pixelratio: {

src/traces/parcoords/lines.js

@@ -87,11 +87,11 @@ function adjustDepth(d) {
     return Math.max(depthLimitEpsilon, Math.min(1 - depthLimitEpsilon, d));
 }
 
-function palette(unitToColor, context, lines_contextcolor, lines_contextopacity) {
+function palette(unitToColor, context, lines_contextcolor, contextOpacity) {
     var result = [];
     for(var j = 0; j < 256; j++) {
         var c = unitToColor(j / 255);
-        result.push((context ? lines_contextcolor : c).concat([context ? lines_contextopacity : 255]));
+        result.push((context ? lines_contextcolor : c).concat([context ? Math.round(contextOpacity * 255) : 255]));
     }
 
     return result;