Revert "Removed PDF from the repo and added a note in the README that describes how to"

This reverts commit f48b2622214084689d5a77dd290d374852e3cb29.
documentation: update with jerasure.org new home

Signed-off-by: Loic Dachary <loic@dachary.org>
Merge branch 'wip-documentation' into 'master'

documentation

updates to replace URLs that do not contain useful information

See merge request !2