ENH: Series from MultiIndex causes segfault
```
In [3]: m = pd.MultiIndex.from_arrays([[1,2], [3,4]])

In [4]: m
Out[4]:
MultiIndex
[(1, 3), (2, 4)]

In [5]: pd.Series(m)
[1]    786 segmentation fault  ipython

pd.Series(m.values) has same fault (list of tuples)
```

Probably this should just be disallowed.
