resolves #341 toc should honor numbered attribute

- toc should include numbers in sections only if numbered attribute is set
- toc should read numbered attribute at position of section (not just global)
- add type="none" attribute to <ol> elements in toc
- add tests and fix incorrect test assumptions
Merge pull request #360 from mojavelinux/toc-numbering

resolves #341 toc should honor numbered attribute