Convert options = {} to **options in the dsl. to remove warnings

lib/quby/compiler/dsl/charting/chart_builder.rb

@@ -16,8 +16,8 @@ module Quby
           @chart_class
         end
 
-        def initialize(questionnaire, key, options = {})
-          @chart = self.class.chart_class.new(key, options)
+        def initialize(questionnaire, key, **options)
+          @chart = self.class.chart_class.new(key, **options)
           @questionnaire = questionnaire
         end
 
@@ -49,7 +49,7 @@ module Quby
           @chart.plotlines << {value: value, color: color}
         end
 
-        def plot(key, options = {})
+        def plot(key, **options)
           unless plottable = @questionnaire.find_plottable(key)
             fail "Questionnaire #{@questionnaire.key} chart #{@chart.key} references unknown score or question #{key}"
           end