append a categorical with different categories to the existing
I just ran into the same problem as the person asking this question on SO

http://stackoverflow.com/questions/29709918/pandas-and-category-replacement

[Jeff](http://stackoverflow.com/users/644898/jeff) gave an excellent answer as usual, I believe he is a pandas developer as well? 

So I was wondering whether something like [hist answer](http://stackoverflow.com/a/29712287/1532474) might be planned to become the default behaviour, when appending Categoricals.
