Return the original message in warnings if they're just a string

Due to the `if` we'd return `nil` if the message was not an array.

Author: carlosmn

lib/docurium.rb

@@ -288,7 +288,7 @@ def initialize(warning, type, identifier, opts = {})
 
     def message
       msg = self._message
-      msg.shift % msg.map {|a| self.send(a).to_s } if msg.kind_of?(Array)
+      msg.kind_of?(Array) ? msg.shift % msg.map {|a| self.send(a).to_s } : msg
     end
   end