Also add a comment to docs/index.rst, pointing folks who are browsing
the source tree (locally, with an editor) at the formatted version on
readthedocs.org .
Also it avoids the failure mode where a user forgets to activate the
virtualenv, types the recommended "pip install" command, and installs
stuff directly to their system instead of safely confined inside the
virtualenv.
* use correct fixed-width-font markup
* fix hyperlinks to neighboring (github-side) .rst files
* refer to python-2.7.11 consistently (thanks to PRab for the catch)
