def configure(opts)
          for key, value in opts
            instance_variable_set "@#{key}", value
          end
          @indent                = opts[:indent] if opts.key?(:indent)
          @space                 = opts[:space] if opts.key?(:space)
          @space_before          = opts[:space_before] if opts.key?(:space_before)
          @object_nl             = opts[:object_nl] if opts.key?(:object_nl)
          @array_nl              = opts[:array_nl] if opts.key?(:array_nl)
          @allow_nan             = !!opts[:allow_nan] if opts.key?(:allow_nan)
          @ascii_only            = opts[:ascii_only] if opts.key?(:ascii_only)
          @depth                 = opts[:depth] || 0
          @quirks_mode           = opts[:quirks_mode] if opts.key?(:quirks_mode)
          @buffer_initial_length ||= opts[:buffer_initial_length]

          if !opts.key?(:max_nesting) # defaults to 100
            @max_nesting = 100
          elsif opts[:max_nesting]
            @max_nesting = opts[:max_nesting]
          else
            @max_nesting = 0
          end
          self
        end
Configure this State instance with the Hash _opts_, and return
itself.