Remove redundant yet unstable test_spectral_lobpcg_mode

The lobpcg mode is already tested in the test_spectral_clustering test.

LinAlgError was raised when executing test_spectral_lobpcg_mode on some
systems depending on the version of the scipy and LAPACK libraries.
TST: more robust test of dropping in Lars
TST: relax warning class checked in lars
TST: lars tests: more brutal ill-conditionning
ENH: make CD Lasso raise ConvergenceWarning
Merge pull request #3030 from ogrisel/fix-lars-drop-for-good-test-failure

Fix LARS drop for good test failure
DOC: clear up the big elastic net confusion (I hope)

Several users have asked for LogReg w/ E-net (e.g. #3023). Did some
additional copyediting.
Merge pull request #3025 from ogrisel/remove-unstable-lobpcg-test

[MRG] Remove redundant yet unstable test_spectral_lobpcg_mode
ENH: stable test + catch warning + pep8
ENH: more robust test_toy_bayesian_ridge_object
ENH: configure travis to also test old numpy & scipy
DOC: add some header doc to the travis scripts
More informative numerical error message in SGD

Also add a test.
cosmit
DOC: Fixed roc_curve docstring

It does not make sense for y_score of roc_curve to be binary.
Merge pull request #3035 from ogrisel/test-sgd-stability-error

[MRG+1] More informative numerical error message in SGD
Merge pull request #3022 from ogrisel/travis-old-numpy-scipy

[MRG] Set travis to test old versions of numpy and scipy too
MAINT remove _label attribute from SVC.

Fixes #1573.
Sparsity via BestSparseSplitter