simtrial 1.0.1

Statistical improvements

• An example of stratified group sequential design is added for the sim_gs_n() function (#336, #343, thanks to @LittleBeannie).

Computational improvements

• The dplyr syntax in sim_gs_n() is replaced with data.table syntax for better speed (#339, thanks to @jdblischak).
• The parallelelly package version is temporarily downgraded to v1.44.0 for successful macOC build. (#341, #338, thanks to @jdblischak).