tuned order of arguments
make baliL and baliR symmetric
split balance into two, clearer etc
removed unclear clause; slower but clearer
paint root black after insert and delete
tuned white space
tuned names and optimized comparison order
added 2-3 trees (simpler and more complete than the version in ex/Tree23)
tuned
added red black trees --HG-- extra : rebase_source : 28e43c87d5eb14090fa401987d8131c2067f6ab7