Added utility to skip tests if running on Travis
Fix labels of inliers vs outliers

At least based on what svm.OneClassSVM does in the example linked from this document, the description was wrong; labels actually assigned are 1/-1 for good/bad respectively, not 0/1.
FIX assert_array_almost_equal for windows tests
Cosmetic: correct latex formula display
DOC: write cost function of logistic regression.

I feel it important to state clearly what is the cost function of the
model because:

    * Some might want to compare their implementation against this one,
    in which case it is important to know exactly what is the form of the
    cost function

    * Furthermore since the models are quite inconsistent in terms of
    notation for the regularization parameter: some models in this
    module penalize by 1/C, others by alpha and others by alpha/2
Merge pull request #3365 from fabianp/master

DOC: write cost function of logistic regression
Link my name to my wordpress blog
Merge pull request #3366 from MechCoder/link-to-blog

FIX: My name was linked to the wrong github account
fixed typo: diriclet -> dirichlet
Merge pull request #3368 from stevetjoa/typo-diriclet

fixed typo: diriclet -> dirichlet
DOC updated installation documentation

Added Canopy and Anaconda.
Removed EPD.
Merge pull request #3369 from NelleV/install_doc

DOC updated installation documentation
DOC: typo, envelop → envelope
Merge branch 'pr/3358'
MAINT Re-order argument to put deprecated one at the end
DOC: add transpose and intercept to formula of logistic regression
DOC adding return type and improving module doc
DOC return types in datasets.lfw
DOC numpydoc convention for Bunch-returning functions

Also cap lines at 80 chars, remove trailing spaces.

As suggested by @jnothman at
https://github.com/scikit-learn/scikit-learn/pull/3316/files#r14269818
Merge branch 'pr/3316'

Fixes #3316.