Merge pull request #2290 from dengemann/more_ica_improvements

[MRG]: improve logcosh function + tests
DOC: few small doc fixes to layout bugs on new website
comments added to the changes
FIX : backport tanh out param in old numpy
DOC typos involving Nyström
revert the tanh fix
Merge pull request #2331 from jaquesgrobler/master

DOC: few small doc fixes to layout bugs on new website
fix sidebar button size staying constant and leaving a mountain of white-space due to expanding/collapsing toctree
fix cut-off ML map
DOC: also point installation menu to stable
DOC copyedit SGDClassifier docstring

Make it clear immediately that this beast fits SVMs by default,
logistic regression if you ask for it.
BUG: FIX Crammer-Singer formulation in the binary case.
Merge pull request #2336 from jaquesgrobler/DOC_fix_whitespace_on_userguide

DOC: fix for tons of whitespace on the user_guide page of new dev-webpage
Better test for auc_score.
Optim for Crammer-Singer formulation in binary case.
Completely avoid for loop in _auc.
commit added for hack-warning
Merge pull request #2337 from jaquesgrobler/DOC_fix_cut_ML_flowchart

fix cut-off ML map - temporary fix with js hack.. must do a proper css fix. leaving issue open
ENH : simplify ProabilisticPCA covariance_ computation + misc in pca.py
ENH : avoid extra alloc in _infer_dimension_ in pca.py