BUG: column name conflict & as_index=False breaks groupby ops

closes https://github.com/pydata/pandas/issues/7115
closes https://github.com/pydata/pandas/issues/8112
closes https://github.com/pydata/pandas/issues/8582

ok, then add the current results after (using the same constructed data). Also pls show the df's here right after you construct them (you can do it in the current results). thxs. This is a nice fix but needs to be explained to users in detail.