Package 0.5.0

• Added forward selection to the psfmi_lr and psfmi_coxr functions.
• Added the functions psfmi_lr_fw, psfmi_lr_bw, psfmi_coxr_fw and psfmi_coxr_bw that are called by psfmi_lr or psfmi_coxr for forward and backward selection after MI with logistic and Cox regression models.
• Extended the function psfmi_perform by including the possibility of using cross-validation in combination with multiple imputation.
• Added the functions cv_MI, cv_MI_RR, MI_cv_naive, boot_MI and MI_boot, that are called by psfmi_perform to combine cross-validation or bootstrapping with MI.
  
• Added the function bw_single for backward selection in a single dataset.
• Added the functions pool_auc, rsq_nagel and scaled_brier.
• Added the internal functions mean_auc_log, clean_P, miceImp.
• Updated vignettes.
• Created a package website with pkgdown.

Package 0.2.0

• Added functions pool_intadj.R, pool_performance.R, psfmi_mm.R, psfmi_mm_multiparm, psfmi_perform, psfmi_stab.
• Added the class statement smodsmi to the functions psfmi_lr, psfmi_coxr
  and psfmi_mm.
• Added the following output object information to psfmi_lr, psfmi_coxr
  and psfmi_mm: model_type, predictors_in, predictors_out, fit.formula, predictors_final and predictors_initial.
• Excluded function miperform_lr.
• Changed name object multiparm_p into multiparm.
• Updated vignettes.