Fix highlighting of cat command [Fix #1225]

lib/pry/commands/cat/abstract_formatter.rb

@@ -8,7 +8,7 @@ class Pry
       def decorate(content)
         content.code_type = code_type
         content.between(*between_lines).
-          with_line_numbers(use_line_numbers?)
+          with_line_numbers(use_line_numbers?).highlighted
       end
 
       def code_type

lib/pry/commands/cat/exception_formatter.rb

@@ -16,7 +16,7 @@ class Pry
         set_file_and_dir_locals(backtrace_file, _pry_, _pry_.current_context)
         code = decorate(Pry::Code.from_file(backtrace_file).
                                     between(*start_and_end_line_for_code_window).
-                                    with_marker(backtrace_line)).to_s
+                                    with_marker(backtrace_line))
         "#{header}#{code}"
       end
 

lib/pry/commands/cat/input_expression_formatter.rb

@@ -20,7 +20,7 @@ class Pry
 
           content
         else
-          decorate(Pry::Code(selected_input_items.first)).to_s
+          decorate(Pry::Code(selected_input_items.first))
         end
       end