Fix the build take 2.

lib/tasks/smoke_test.rake

@@ -41,7 +41,7 @@ task "smoke:test" do
     raise "TRIVIAL GET FAILED WITH #{response.code}"
   end
 
-  results = ""
+  results = +""
 
   IO.popen("node #{Rails.root}/test/smoke_test.js #{url}").each do |line|
     puts line

plugins/discourse-narrative-bot/lib/discourse_narrative_bot/dice.rb

@@ -10,7 +10,7 @@ module DiscourseNarrativeBot
         return I18n.t('discourse_narrative_bot.dice.invalid')
       end
 
-      output = ''
+      output = +''
 
       if num_of_dice > MAXIMUM_NUM_OF_DICE
         output << I18n.t('discourse_narrative_bot.dice.not_enough_dice',