NF: Add Massively Univariate Linear Model with permuted OLS.

An example is still needed and more tests may be welcomed.
cosmetic changes in permuted_ols + rename module.
Mass univariate: Add Haxby example.
Mass univariate -- permuted OLS: address PR comments.
permuted OLS: Correct doctests + C-contiguousity with copy()
Permuted OLS: fix contiguousarray problem (one check was missing).
permuted OLS: Modify example --> add thresholded F-score for comparison.
permuted OLS: adjust memory pre-allocation + robust sparsity threshold.
permuted OLS: add intercept by default + unit tests + code robustness.
permuted OLS: backport for sklearn f_regression.
permuted OLS: commit forgotten files (_utils/fixes directory).
permuted OLS: add support for sklearn < 0.12 (no sparse matrix support)
permuted OLS: Add documentation + commit forgotten test_gsarray.py
permuted OLS: fix gsarray tests for Travis (raises *several* warnings)
permuted OLS: fix test again for Travis.
permuted OLS: Magnify doc.
permuted OLS: typos + cosmit.
BF: Being more precise in checking sklearn version in _utils/fixes.
Integrate GaelVaroquaux"s comments on PR.
Cosmit: rename "append_iter_data" in "append".