v0.3.0

Changed

• The last body field is the rest of the document, verbatim: it is never
  parsed or trimmed, so it may hold top-level --- lines, setext underlines,
  tables, and fences. Before, such a body was written and then refused on read
  (found 2 sections) or cut.
• Body text is verbatim in both directions: no line break is added at the end
  of the document or removed from a section. Documents written by 0.3.0 end
  with the last byte of the last section.
• The presence of the last body field is its separator: no separator is
  None, a separator followed by nothing is Some(""), and "" after it is
  literal text. The "" convention for Some("") remains only for optional
  body fields that are not the last.
• Front-matter keys are written in declaration order (proto field order for
  buffa messages) in YAML, JSON, and TOML, not alphabetically. No dependency
  was added.
• A bare first slice that is not a mapping is body from its first byte; the
  leading whitespace and --- prefix is discarded only before fields.

Added

• A body value that is not the last and holds a top-level --- line, an
  unclosed fence, or a trailing carriage return is ErrorKind::Body at write
  time, instead of a document that cannot be read back.