RDoc autolinks the word "Rails" to the doc page for the Rails module.
But README.rdoc is displayed in the home page at GitHub and the slashes
are visible there, which is weird. We leave by now the slashes off in
the file, and generate a second file for the API with them.
* Removes spurious markup from code blocks
* Integrates code blocks into ordinary paragraph flow
* Change link to the Rails Tutorial so that it points directly to the book
* Use proper RDoc markup for links