Aredis

* sync optimization of scripting from redis-py made by [bgreenberg](https://github.com/bgreenberg-eb) --> [related pull request](https://github.com/andymccurdy/redis-py/pull/867)

* sync bug fixed of `geopos` from redis-py made by [categulario](https://github.com/categulario) --> [related pull request](https://github.com/andymccurdy/redis-py/pull/888)

* fix bug which makes pipeline callback function not executed
* fix error caused by byte decode issues in sentinel
* add basic transaction support for single node in cluster
* fix bug of get_random_connection reported by myrfy001

* fix bug of pubsub, in some env AssertionError is raised because connection is used again after reader stream being fed eof
* add reponse decoding related options(`encoding` & `decode_responses`), make client easier to use * add support for command `cluster forget`
* add support for command option `spop count`