Add --plot-to-board to plot command

This flag of plot command will send the plotted burndown chart to the first
card of the `Done` column.

close openSUSE#134

lib/cli.rb

@@ -189,13 +189,24 @@ def burndown
     end
   end
 
-  desc 'plot SPRINT-NUMBER [--output] [--no-tasks] [--with-fast-lane]', 'Plot burndown chart for given sprint'
+  desc 'plot SPRINT-NUMBER [--output] [--no-tasks] [--with-fast-lane] [--plot-to-board]', 'Plot burndown chart for given sprint'
   option :output, aliases: :o, desc: 'Output directory', required: false
   option 'with-fast-lane', desc: 'Plot Fast Lane with new cards bars', required: false, type: :boolean
   option 'no-tasks', desc: 'Do not plot tasks line', required: false, type: :boolean
+  option :plot_to_board, type: :boolean, desc: 'Send the plotted data to the first card of Done column'
   def plot(sprint_number)
     process_global_options options
-    BurndownChart.plot(sprint_number, options)
+    if options[:plot_to_board]
+      begin
+        chart = BurndownChart.new @@settings
+        chart.update(options)
+      rescue TrolloloError => e
+        STDERR.puts e
+        exit 1
+      end
+    else
+      BurndownChart.plot(sprint_number, options)
+    end
   end
 
   desc 'backup', 'Create backup of board'