New faithful dataset.

The previous faithful dataset (oldfaithful) had some non-numerical
values, which is cumbersome. This dataset does not have this limi-
tation and is the same that ships with the R package.

From: Fabian Pedregosa <fabian.pedregosa@inria.fr>

git-svn-id: https://scikit-learn.svn.sourceforge.net/svnroot/scikit-learn/trunk@411 22fbfee3-77ab-4535-9bad-27d1bd3bc7d8