simtrial 1.0.0

Statistical improvements

• Provide the updated boundary for objects generated by sim_gs_n() (#255, thanks to @LittleBeannie).
• Users can now pass a formula to call the wlr() function (#280, thanks to @jdblischak).
• wlr() is now a S3 class method for both tte_data class and counting_process class
  (@276, #280, @281, thanks to @jdblischak)
• The randomization ratio is output as attributes of sim_pw_surv()
  (#279, #311 thanks to @LittleBeannie and @jdblischak).

Documentation

• Add 3 vignettes introducing simulation of fixed or group sequential design
  via a single function call of sim_fixed_n() and sim_gs_n() or from the ground up
  (#302, #316, thanks to @LittleBeannie).
• Add a vignette discussing the potential discrepancies between simtrial and survdiff
  (#308, thanks to @larry-leon).
• Update parallel vignette to address data.table multithreading (#319, thanks to @jdblischak).

Speed improvements

• Optimize parallel simulation speed in sim_fixed_n() and sim_gs_n() by
  replacing foreach(.combine = "rbind") with manual data frame combination
  (#318, thanks to @nanxstats).