(PECL tokyo_tyrant >= 0.2.0) Move to next key
(PECL tokyo_tyrant >= 0.2.0) Returns the current key
(PECL tokyo_tyrant >= 0.2.0) Get the current value
(PECL tokyo_tyrant >= 0.2.0) Construct an iterator
(PECL tokyo_tyrant >= 0.2.0) Rewinds the iterator