Use chart_class instead of class_chart (for user)

Author: Prakriti-nith

lib/daru/view/adapters/googlecharts.rb

@@ -51,8 +51,8 @@ def init_table(data=[], options={}, user_options={})
         # @param user_options [Hash] Extra options provided by the user like class_chart
         # @return [String] The class of the chart (Chart, Charteditor or Chartwrapper)
         def get_class_chart(user_options={})
-          return 'Chart' if user_options[:class_chart].nil?
-          user_options.delete(:class_chart).to_s.capitalize
+          return 'Chart' if user_options[:chart_class].nil?
+          user_options.delete(:chart_class).to_s.capitalize
         end
 
         # @param data [Array, Daru::DataFrame, Daru::Vector, Daru::View::Table]