DOC: added Machinalis testimonial
COSMIT smipler & more robust check in test_kfold_valueerrors

Using assert_warn_message internally cleans the warning
registries making this test more robust to changes in other tests.
DOC fix see also references
Merge pull request #3491 from ogrisel/fix-warning-test-cross-val

[MRG] TST unstable warning test in test_kfold_valueerrors
DOC fix see also reference
DOC fix markup error
MAINT fix prng in test_f_oneway_ints

Not fixing the PRNG cause the test to fail randomly under windows
where the 4 decimals place check can be too strict for some unlucky
random draws of test data.
ENH Stochastic Coordinate Descent for ElasticNet & Lasso