change parcats_hoveron_color to include count in hoverinfo

Author: weiweikee

Diff for: test/image/mocks/parcats_hoveron_color.json

@@ -3,7 +3,7 @@
     {"type": "parcats",
       "domain": {"x": [0.125, 0.625],"y": [0.25, 0.75]},
       "hoveron": "color",
-      "hoverinfo": "probability",
+      "hoverinfo": "count+probability",
       "dimensions":[
         {"label": "One", "values": [1, 1, 2, 1, 2, 1, 1, 2, 1]},
         {"label": "Two", "values": ["A", "B", "A", "B", "C", "C", "A", "B", "C"]},