TST add common test to check if estimators overwrite their init params
ENH use only a few samples in test.
FIX in tree and ensemble: don't overwrite random state in fit.
FIX don't overwrite random_state in fit in EllipticEnvelope
FIX don't modify random_state in clustering algorithms.
ENH make code more clear: MiniBatchKMeans only uses random_state in first run of partial_fit.
FIX in ward: don't overwrite n_components.
FIX remaining parameter issues in GradientBoosting
TST took the safty off the tests ;)