stringr 1.4.0

• str_interp() now renders lists consistently independent on the presence of
  additional placeholders (@amhrasmussen).

• New str_starts() and str_ends() functions to detect patterns at the
  beginning or end of strings (@jonthegeek, #258).

• str_subset(), str_detect(), and str_which() get negate argument,
  which is useful when you want the elements that do NOT match (#259,
  @yutannihilation).

• New str_to_sentence() function to capitalize with sentence case
  (@jonthegeek, #202).