working on tree markers

--HG--
branch : develop
working on tree markers

--HG--
branch : develop
fixing CI

--HG--
branch : develop
fixing CI

--HG--
branch : develop
fixing CI

--HG--
branch : develop
changing tree API

--HG--
branch : develop
fixing CI

--HG--
branch : develop
Merge branch 'master' of https://github.com/dahpgjgamgan/alvi into dahpgjgamgan-master

Conflicts:
	alvi/client/containers/tree.py
	alvi/config.py
merging red-black trees
removing random fail in binary search
working on config
working on config
working on postpone_sync context manager in client containers
adding method MultiMarker.remove
adding new scenes
moving change root functionality from Tree to RBTree
moving change root functionality from Tree to RBTree
fixing tests
working on graph
Update README.md