message: fix(jekyll): Make frontmatter parser strict
  Jekyll has a different frontmatter format than cobalt.  The converter
  was designed to handle both.  This tightens that to only support
  jekyll's.
diff: @@ -167,21 +167,14 @@ fn split_document(content: &str) -> Result<(Option<&str>, &str)> {
  let second = splits.next().unwrap_or("");
  let third = splits.next().unwrap_or("");
  - if third.is_empty() {
  - // only one "---"
  - if first.is_empty() {
  - Ok((None, second))
  - } else {
  - Ok((Some(first), second))
  + if !first.is_empty() {
  + bail!("Invalid leading text in frontmatter: {:?}", first);
  }
  - } else {
  - // first should be empty
  if second.is_empty() {
  Ok((None, third))
  } else {
  Ok((Some(second), third))
  }
  - }
  } else {
  Ok((None, content))
  }
  @@ -229,7 +222,6 @@ mod test {
  }
  #[test]
  - #[ignore] // TODO(epage): This should pass
  fn split_document_empty_content() {
  let fixture = "---\ntitle: test_post\n---\n";
  