Flask-redis-sentinel

* Connections are now thread-local to avoid race conditions after Redis master failover
* Removed support for REDIS_{HOST, PORT, DB} config variables

URL parsing code was split to a separate library `Redis-Sentinel-Url` and this release uses the library.
BC incompatible change when connecting to slaves in a default connection:


Old
redis+sentinel://host:port/service?slave=true


Should now be written as:


New
redis+sentinel://host:port/service?client_type=slave

- Use config variables other than REDIS_{HOST, PORT, DB} even if REDIS_URL is used
- Minor refactoring

- Initial release