BUG: stacking multiple levels

[jreback]

from #7653
cc @bluefir

df = DataFrame(np.random.randn(1000, 27), 
               columns=MultiIndex.from_tuples(list(
                                   itertools.product(xrange(3), repeat=3))))
df.stack(level=[1, 2])

should be equiv to:

df.stack(level=1).stack(level=1)

but is raising