parse_format (Spec::Runner::Options)

    # File lib/spec/runner/options.rb, line 197
          def parse_format(format_arg)
            format, where = ClassAndArgumentsParser.parse(format_arg)
            unless where
              raise "When using several --format options only one of them can be without a file" if @out_used
              where = @output_stream
              @out_used = true
            end
            @format_options ||= []
            @format_options << [format, where]
          end