explicit writerHighlight=True

Because pandoc issue 906 and Pull Request 907 makes to prevent implicit
syntax highlighting for HTML output.
Merge pull request #15 from cosmo0920/explicit-writerHighlight

explicit writerHighlight=True
Bump dependency versions
Add upper bound on temporary

- https://github.com/batterseapower/temporary/pull/12
Write PersistFieldSql instance by hand

Fixes #16
Version bump