Improve Post Format Archive heads. Follows up on #95 and https://github.com/Automattic/_s/commit/e3b4907946696c324877b775bdfea8314af1799a#diff-ff638db82c6ac72a05781ba3e086fdf0L48.
Merge pull request #344 from Automattic/add-all-post-format-headings

Improve Post Format Archive Headings. Props @philiparthurmoore