Merge pull request #1 from GaelVaroquaux/pr_219

ENH: more robust backports
deleted sparse_variation directory
BF: broken SL haxby demo script
ENH: add support for vmax in plot_stats_map
Tiny doc fixes in decoding.rst (and a few whitespace changes)
For consistency use visuali*z*ation rather than visuali*s*ation
Main fix on l. 179 for >>> folding in the doc. Plenty of other whitespace differences
Fix RHS "Table Of Contents" link which was pointing to index.html rather than user_guide.html
ENH: renamed operators.py ==> proximal_operators.py
mergec _cv_tricks.py into cv.py
REFACTOR: renamed smooth_lasso.py ==> space_net_solver.py
ABSTRACTION: removed plotting code from cv.py
REFACTOR: merged tv.py into space_net_solvers.py
REFACTOR: renamed cv.py ==> space_net.py
BF: broken refactoring
broken examples
ENH: accept vmax in plot_anat
Fix typo (plus some whitespace differences)
ENH: check_niimg ensure_3d works on filename

nifti_masker now complains for non 3d masks
BUG: mmap_mode='r' and Nifti1Image

tricky interaction with mmap_mode='r' that renders internal structures of
Nifti1Image read-only and as a result they don't save anymore