RF: sklearn compatibility -- use new name l1_ratio instead of rho

to prevent annoying DeprecationWarning ;)
BF: import externals not only in __debug__
TST: do not test all dependencies upon setup_module unless MVPA_TESTS_VERBOSITY>=2

otherwise nosetests-ing any(!) test  goes  through testing of all dependencies
which is imho overkill and slows us down.  All make unittest* Makefile targets
do not use nosetests cmdline yet and by default are verbose enough to have them
tested
TST: do not rely on knowing repr of a dictionary (order varies) while testing AttributeMap repr

Was detected with daily_tests against python3 where elements had different order
TST(PY3): another workaround np.unique on arrays with None -- do not rely on the order of splits while testing
BF: provide flush for our stdout wrapper so it would be found
NF: minimal dataset from voxel selection
BF: resolve merge conflict