create red/black trees
red/black check functions
WIP; split insert & repaint functions
add pointer to parent
dont pass what can be calculated; remove unnecessary args
WIP: insert progress
insert *untested*
fix tree root when rotating nodes
additional insert tests
+lookup node; WIP: delete
handle more deletion cases & add tests
handle deleting root in existing cases
remove root in otherwise empty tree
rename rb_tree_recolor to rb_tree_ins_recolor
use generic rotate_left & rotate_right functions
get descriptive status from tree verification functions & write tests for it
delete black node from red parent
remove old code
more rm cases
WIP: first few del rebalancing cases