#28 Directories randomly get deleted.

[Daniel Miller]

If a file is deleted, the leftmost child in the RB tree has it's sub directories wiped out.
The following test shows this bug:

[TestMethod]
public void CompoundFile_Delete_ChildElementMaintainsFiles()
{
  using (var compoundFile = new CompoundFile())
  {
    var storage1 = compoundFile.RootStorage.AddStorage("1");
    var storage2 = compoundFile.RootStorage.AddStorage("2");
    var storage3 = compoundFile.RootStorage.AddStorage("3");
    storage1.AddStream("1.1");
    compoundFile.RootStorage.Delete("2");
    storage1 = compoundFile.RootStorage.GetStorage("1");
    storage1.GetStream("1.1");
  }
}