Use parse-markdown not read-markdown.

As of markdown v0.12, `parse-markdown` ensures \r\n -> \n
conversion (but `read-markdown` does not).
Bump to v0.14
Merge pull request #68 from pb82/master

added missing </div> tag in page-template
Reuse a single namespace for templates

Gains back speed lost in commit 14710bb and commit 07c1f8d

Roughly 4X faster
Add very verbose message about Racket doc cache

This way, it's clearer why it "pauses" upon encountering the first file
that uses a Racket doc ref.
Bump to v0.15, requiring markdown v0.13
Support .html post source files. Closes #72.
Delete "logos".
Fix link
travis-racket v0.5 and Racket 6.0