Converted to markdown with Pandoc ...

* http://johnmacfarlane.net/pandoc/
* pandoc -f html -t markdown index.html > index.md
Removed stale links, darcs repo, stale asdf-install info (no signed
tarball location)
added dead-link marker & prepped for README.md format
moved up to date documentation to README.md
removed hardlink to API doc
Merge pull request #1 from nickyp/make-github-canonical-for-s-http-client

Make github README canonical for s-http-client