v0.5.0

The catalog grows from 49 rules to 50, and check becomes the default
command.

Changed

• A first argument that is not a command name is now taken as a path, so
  sloplint draft.md and sloplint - scan instead of failing with
  unknown command. A mistyped command fails as a missing file, still exit 2.

New rules

• trailing-significance-participle (structure, warning): the participle
  clause hung off the end of a sentence to say what a fact means, "the sign
  carries both names, showcasing the range of travellers it draws". An event
  cannot showcase anything, so the claim belongs to a narrator who never
  appears in the text.

  The verb list is closed and narrow: highlighting, showcasing,
  reinforcing, shaping, enhancing, cementing, solidifying,
  embodying, fostering, facilitating, signalling. Verbs humans write
  in the same position -- driving, representing, reflecting, marking,
  contributing, illustrating, demonstrating, emphasising, echoing,
  affirming -- stay out, because they usually take a person as the subject
  and a regex cannot see the subject. underscoring is left to
  underscores-highlights.

  Two guards drop gerund lists: a preceding -ing word means the match is a
  middle list item, and a following comma, "and" or "or" means it is not the
  last item. "signalling to" is the physical gesture and does not flag.