Added test_regressor_pickle to tests.
Added test_classifiers_pickle to tests.
Finished adding pickle tests.
Removed the use of StringIO, using pickle.dumps instead.
FIX rebasing trouble in common tests: the meaning of dont_test changed
FIX don't compare strings with "is". that is really not robust!
ENH in transformer pickle test, only test transformers that provide a 'transform' method. and only test that.
ENH in common tests, use long variable names for all tests
FIX remove all unseeded random variables from common tests.