Simple variable rename.
Rearrange tests so that the common case is first.
1. Optimize the case when deleting elements that are not present in the tree.  We know just return the same tree with no allocation.
2. Optimize singleton constructor.
3. Add a test for point (1).
Some code rearrangment.
Package visibility for verifyRedBlackProperties.
Remove old comment.
1. Implement method fromSortedArray() that constructs a red-black tree from a sorted array.
2. Implement some testing utilities.
3. Added the ilog() function (base 2).