Display identifiers and lists at the repl

lib/chervil/repl.rb

         "(#{obj.elements.map { |el| display(el) }.join(' ')})"
       when AST::Quotation
         "\'#{display(obj.value)}"
+      when AST::Identifier
+        obj.name
       when Float
         if obj.floor.to_f == obj
           obj.to_i
         else
           obj
         end
+      when Array
+        "(#{obj.map { |el| display(el) }.join(' ')})"
       else
         obj
       end