update migration
update migration

we don't have a legacy api (yet) so just point users to [1.1.14](https://github.com/pysal/pysal/releases/tag/v1.14.4) if they need Python 2 support.
lixun910/pysal,lixun910/pysal,weikang9009/pysal,lixun910/pysal,sjsrey/pysal,lanselin/pysal,pedrovma/pysal,pysal/pysal