reorganize branches.

Seem like the branch on the repo are weird.

4.x exist, but seem to have been a 4.3.x, some commit of 4.3 arenot in master.

I've now pushed 4.x as a new 4.3.x which tip is currently 2bbc8fde4bb12d8643969ece87c74041134f4990 (from 2016).

I'm going to push 4.9.0 (5a5deba63c4c1d49ff46289e050777a4103a6311) as the new 4.x (as it will be the python 2 compatible branch).