made a simple deceiptive test function for big data problems
added a test for covariance functions
made a test that hyper parameter sampling works precisely as in spearmint
entropy_search_big_data: enriched comments and changed scaling
optsizechooser: explicitly set and report seed
gp_model: fixed bug, added covariance function BigData
hyper_parameter_sampling: improved logging, set spearmint standard value
abstract_test: improved :)
ei_test: fixed bug in gradient test
gp_test: moved covariance tests to extra file (see above)