This commit is adding support of data compression.
LZF was choosen because it small and fast and Redis server uses it.
Since [pecl package](https://pecl.php.net/package/lzf) doesn't provide
lzf.h file after installing, LZF library was added as submodule.
Another algorythms may be easely added by analogy with serializers.
TODO: unit-tests for different data types.