Fix assignment of attribute uninteger_is_from by to_integer()

[jdblischak]

This is a follow-up to my big refactor of the S3 classes in #584. I missed the use of class(x) at the end of to_integer() to assign the attribute uninteger_is_from. This caused the wrong value of uninteger_is_from to be assigned because the method is no longer embedded in the class hierarchy.

gsDesign2/R/to_integer.R

Lines 579 to 592 in 5103d9c

	# Add attributes to x_new to identify whether it is a gs_design_ahr orbject or gs_power_ahr object
	if ("analysis_time" %in% names(x$input) && "info_frac" %in% names(x$input) && "ahr" %in% class(x)) {
	attr(x_new, 'uninteger_is_from') <- "gs_design_ahr"
	} else if ("analysis_time" %in% names(x$input) && "event" %in% names(x$input) && "ahr" %in% class(x)) {
	attr(x_new, 'uninteger_is_from') <- "gs_power_ahr"
	} else if ("analysis_time" %in% names(x$input) && "info_frac" %in% names(x$input) && "wlr" %in% class(x)) {
	attr(x_new, 'uninteger_is_from') <- "gs_design_wlr"
	} else if ("analysis_time" %in% names(x$input) && "event" %in% names(x$input) && "wlr" %in% class(x)) {
	attr(x_new, 'uninteger_is_from') <- "gs_power_wlr"
	} else if (!("n" %in% names(x$input)) && "rd" %in% class(x)) {
	attr(x_new, 'uninteger_is_from') <- "gs_design_rd"
	} else if ("n" %in% names(x$input) && "rd" %in% class(x)) {
	attr(x_new, 'uninteger_is_from') <- "gs_power_rd"
	}

While writing a test for this, I discovered that to_integer() is unable to process the object returned by gs_power_rd() because it doesn't have the element input with the values of its input arguments. I went ahead and fixed that too.

[LittleBeannie]

Thank you, @jdblischak! I got it merged.