changed '<<' to '+=' to support frozen strings

bot.rb

@@ -8,10 +8,10 @@ require 'rufus-scheduler'
 def random_quote(quotes)
   entry = quotes.keys.sample
   quote = "**Quote of the Day**\n"
-  quote << "From the #{quotes[entry][:tech]}: #{entry}\n"
-  quote << '```'
-  quote << quotes[entry][:quote]
-  quote << '```'
+  quote += "From the #{quotes[entry][:tech]}: #{entry}\n"
+  quote += '```'
+  quote += quotes[entry][:quote]
+  quote += '```'
 end
 
 # map quote types