Into test

This starts a comprehensive test of into.  In particular it makes sure that `into` maps these data-structures into each other cleanly.

```Python
L = [[100, 1, 'Alice'],
     [200, 2, 'Bob'],
     [300, 3, 'Charlie']]

df = DataFrame(L, columns=['amount', 'id', 'name'])

x = np.array(list(map(tuple, L)), dtype=[('amount', 'i8'), ('id', 'i8'), ('name', 'U7')])

arr = nd.array(L, dtype='{amount: int64, id: int64, name: string}')

bc = bcolz.ctable([np.array([100, 200, 300], dtype=np.int64),
                   np.array([1, 2, 3], dtype=np.int64),
                   np.array(['Alice', 'Bob', 'Charlie'], dtype='U7')],
                  names=['amount', 'id', 'name'])
```

I plan to extend this over time but for the moment I'd like to get it in quickly.