Groupby - Apply method doesn't handle arguments correctly
The `apply` method on a groupby object appears to send all arguments to the applied function. As in, if you try to do `df.groupby(level='dt').apply(func, axis=1)`, the `axis=1` argument is passed to `func` rather than being parsed by `apply` as intended. The behavior is correct, however, in the `DataFrame.apply` method.
