grouped.filter with axis=1 gave filtered rows
using pandas 0.16.2
minimum example here:

```
import numpy as np
import pandas as pd

index = pd.MultiIndex.from_product([range(10), [0, 1]])
data = pd.DataFrame(np.arange(100).reshape(-1, 20), columns=index)
data.groupby(level=0, axis=1).filter(lambda x: x.iloc[0, 0] > 10)
```

expected: get all filtered (grouped) columns as a DataFrame
result: `IndexError`

when change `np.arange(100)` to `np.arange(1000)` (more rows than columns)
results data frame with missing rows.
