forcats 0.5.0

• as_factor() gains a logical method that always returns a factor with
  levels "FALSE" and "TRUE" (#185).

• fct_c(), fct_collapse() and fct_recode() are now explicitly
  documented as using dynamic dots
  (@labouz, #234).

• fct_collapse() now accepts a other_level argument, to allow a
  user-specified Other level (@gtm19, #194). It now correctly collapses
  factors when other_level is not NULL (#172), and makes "Other" the
  last level (#202) (@gtm19, #172 & #202)

• fct_count() no longer converts implicit NAs into explicit NAs (#151).

• fct_inseq() behaves more robustly when factor levels aren't all numbers
  (#221).

• fct_lump() has been split up into three new functions: fct_lump_prop(),
  fct_lump_n(), and fct_lump_lowfreq(). (@jonocarroll, #167, #142).
  All fct_lump_() functions check their inputs more carefully
  (@robinson_es, #169)

• fct_reorder2() gains a helper function first2(), that sorts .y by the
  first value of .x (@jtr13).