Extract chart value object

This simplifies the views (slightly).

app/models/stats/chart.rb

@@ -0,0 +1,18 @@
+module Stats
+
+  class Chart
+
+    attr_reader :action, :height, :width
+    def initialize(action, dimensions = {})
+      @action = action
+      @height = dimensions.fetch(:height) { 250 }
+      @width = dimensions.fetch(:width) { 460 }
+    end
+
+    def dimensions
+      "#{width}x#{height}"
+    end
+
+  end
+
+end