Wijisqs

- bugfix; broker drain duration ought to be a float.

implemented clean shutdown: https://github.com/komuw/wijisqs/pull/32

- shard/separate all state per queue: https://github.com/komuw/wijisqs/pull/30
- use one `botocore` client per thread: https://github.com/komuw/wijisqs/pull/31

- one `wijisqs.SqsBroker` instance should be able to serve multiple queues: https://github.com/komuw/wijisqs/pull/26

- bugfix, make sure QueueUrl is always available: https://github.com/komuw/wijisqs/pull/23
- for empty queues, sleep exponetially upto maximum : https://github.com/komuw/wijisqs/pull/24

- bugfix; fix keyError on empty queues : https://github.com/komuw/wijisqs/pull/18
- for the same instance of a `wijisqs.SqsBroker`; create queue and tag queue should only run once : https://github.com/komuw/wijisqs/pull/19