ECML/PKDD: link to paper directly instead of workshop website

Used the U. Liège URL instead of the UvA one -- the latter
doesn't require clicking a license, but I just left UvA so
I'm not sure how long I can keep the URL.
Merge pull request #1 from larsmans/patch-1

ECML/PKDD: link to paper directly instead of workshop website
Merge pull request #2 from glouppe/master

Tentative abstract (work in progress)
Merge branch 'master' of github.com:jakevdp/NIPS2013_sklearn
ENH: reorganize content
Wordings