ADD logistic regression with crossvalidation

This PR adds a logistic regression benchmark using crossvalidation that allows to evaluate one fold at a time.

Furthermore it:

Fixes a typo leading to a crash when using trying to load data for logistic regression
Introduces "rng" as a further argument to objective_function/objective_function_test (related to #2)
Fixes some PEP-8 issues

NOTE: This PR can only be merged after add-auto-sklearn is merged. As it is it fails unittests because of scikit-learn version conflicts

automl / HPOlib1.5