v0.7.1

Fixed

• The README's ## Output table lists mermaid and json. It had not, since
  both were added, so the first place a reader looks to find out what the tool
  can produce named five formats out of seven. A test now checks the table
  against ALL_FORMATS: the existing guard covers flag names, not the values a
  flag accepts, which is how the table fell behind twice without failing.