Major changes

MAINT #192: SMAC uses version 0.4 of the random forest library pyrfr. As a side-effect, the library swig is necessary to build the random forest.
MAINT: random samples which are interleaved in the list of challengers are now obtained from a generator. This reduces the overhead of sampling random configurations.
FIX #117: only round the cutoff when running a python function as the target algorithm.
MAINT #231: Rename the submodule smac.smbo to smac.optimizer.
MAINT #213: Use log(EI) as default acquisition function when optimizing running time of an algorithm.
MAINT #223: updated example of optimizing a random forest with SMAC.
MAINT #221: refactored the EPM module. The PCA on instance features is now part of fitting the EPM instead of reading a scenario. Because of this restructuring, the PCA can now take instance features which are external data into account.

Minor changes

SMAC now outputs scenario options if the log level is DEBUG (2f0ceee).
SMAC logs the command line call if invoked from the command line (3accfc2).
SMAC explicitly checks that it runs in python>=3.4.
MAINT #226: improve efficientcy when loading the runhistory from a json file.
FIX #217: adds milliseconds to the output directory names to avoid race. conditions when starting multiple runs on a cluster.
MAINT #209: adds the seed or a pseudo-seed to the output directory name for better identifiability of the output directories.
FIX #216: replace broken call to in EIPS acqusition function.
MAINT: use codecov.io instead of coveralls.io.
MAINT: increase minimal required version of the ConfigSpace package to 0.3.2.