solution to depth-first-search
address comments raised in issue #46 (https://github.com/ocaml/ocaml.org/pull/480#issuecomment-43432958)
improve in light of further review comments
more improvements thanks to christophe's review
don't bother with record for graph representation any longer - overkill
make tuple at call site, not when building initial state
Complete the list of programs to remove with "clean"
Allow O2wUniverse.of_repositories during staging

This function may fail due to a discrepancy between the installed OPAM
version (say compiled from the Git repository) and the opam2web
package.  This should not hinder testing the site on a local machine,
it should only fail on the server.
Use SVG version of RSS icon when possible
Depend on opam_update_list and not the program generating it

It prevents the file to be used while it is generated provoking the
following error "execvp: script/generate_opam_update_list: Text file
busy" when compiling with "make -j".
Make the RSS icon gray
contributors.md: add Rackspace

Addresses #483.
Planet: without <pre> allow code to wrap
grammar fix and simplify print
companies.md: put top quote into grid
companies.md: add ForAllSecure

Closes #466.
companies.md: add Ahrefs

Closes #449.
phrase as fold; incorporate christophe's feedback
further simplifications
further simplifications