.gt() add support for single column dataframes
It would be great if when comparing df to series like in pandas .gt() or .lt() one could compare also to single column dataframes instead of series.
Maybe also extend it to other functions?

Thanks



This works:
```
df1 = pd.DataFrame(np.array([[2,2],[1,1], [0,0]]), columns = ['a1','a2'])
df2 = pd.Series([2,2,2], name = 'b')
df1.lt(df2, axis=0)
```

This doesnt
```
df1 = pd.DataFrame(np.array([[2,2],[1,1], [0,0]]), columns = ['a1','a2'])
df2 = pd.DataFrame([2,2,2], columns = ['b'])
df1.lt(df2, axis=0)
```

