use 'title.text' in mocks

Author: etpinard

test/image/mocks/gl3d_reversescale.json

@@ -8,7 +8,7 @@
     ],
     "reversescale": true,
     "colorbar": {
-      "title": "surface",
+      "title": {"text": "surface"},
       "x": -0.15,
       "len": 0.3,
       "y": 0.7
@@ -31,7 +31,7 @@
     "intensity": [0, 0.33, 0.66, 1],
     "reversescale": true,
     "colorbar": {
-      "title": "mesh3d",
+      "title": {"text": "mesh3d"},
       "x": -0.15,
       "len": 0.3,
       "y": 0.4
@@ -130,15 +130,15 @@
     ],
     "reversescale": true,
     "colorbar": {
-      "title": "streamtube",
+      "title": {"text": "streamtube"},
       "x": -0.15,
       "len": 0.3,
       "y": 0,
       "yanchor": "bottom"
     }
   }],
   "layout": {
-    "title": "gl3d trace with reversescale:true",
+    "title": {"text": "gl3d trace with reversescale:true"},
     "scene": {
       "camera": {
         "eye": {"x": -2, "y": -0.35, "z": 0.34}