v1.0.6: Some memory optimization (#7)

* reverse iterator init

* some fixes

* fix reverse iterator seaklowerbound

* fix tests

* fix track channels

* longest prefix on txn

* some fixes

* revisit

* todo revisit

* major code refactor

* some minor fixes

* add lru

* fix bugs

* added walk func

* add more tests

* some prog

* some progress track mutate

* some progress

* fix tests

* some optimizations

* some memory optimizations