Aioredis-models

* Add support for transactions (14)
* Make `RedisDoubleHash` more atomic and transactional (15)
* Replace `Set` with `List` as applicable in `RedisSet` and `RedisDoubleHash` (16)

* Add enqueue and dequeue to RedisList (13)

* Refactor RedisList.find_index to use enumerate 12

* Add ability to enumerate lists and hashes 11

* allow specifying encoding on RedisString.get

- claim support for Python 3.6+