Merge branch 'mm/readme-markdown'

README has been renamed to README.md and its contents got tweaked
slightly to make it easier on the eyes.

* mm/readme-markdown:
  README.md: move down historical explanation about the name
  README.md: don't call git stupid in the title
  README.md: move the link to git-scm.com up
  README.md: add hyperlinks on filenames
  README: use markdown syntax