Add Skip Lists and Naive Test.
Finished Skip Lists
Fixed Skip Lists search
Ajust test code using 'type erasure'

http://www.cplusplus.com/articles/oz18T05o/
Abstract Rotate Functions
Add SBT.

TODO: delete, rank, select.
Fixed predecessor/successor Exceptions
Add SBT delete, but big N has a bug.
Fixed AVL balanced bug
minor fix
Add getNth to SBT
Add red_black_tree based on std::set
Commit for merge

Next: Augmenting BT
Merge branch 'nightly'