Merge branch 'master' into protocol-support

diff --cc httpx/__init__.py
Simple merge

diff --cc httpx/concurrency/asyncio.py
index a87c9a1d8b8a341020ecdc6e85ca01b8f17cd4cb,6c5dc0c481284d8e80a57a3822620c19fca68129..613d48f9e28778ecf887fa628d9346ba6c73df55
--- 1/httpx/concurrency.py
--- 2/httpx/concurrency/asyncio.py
+++ b/httpx/concurrency/asyncio.py
@@@ -14,9 -14,9 +14,9 @@@ import ss
  import typing
  from types import TracebackType
  
- from .config import PoolLimits, HTTPVersionConfig, TimeoutConfig
- from .exceptions import ConnectTimeout, PoolTimeout, ReadTimeout, WriteTimeout
- from .interfaces import (
 -from ..config import PoolLimits, TimeoutConfig
++from ..config import PoolLimits, HTTPVersionConfig, TimeoutConfig
+ from ..exceptions import ConnectTimeout, PoolTimeout, ReadTimeout, WriteTimeout
+ from ..interfaces import (
      BaseBackgroundManager,
      BasePoolSemaphore,
      BaseReader,

diff --cc httpx/dispatch/connection.py
index 230afc06acea63f72f97b1be03fe9634594f016c,9dda06d0317831591880dea1d112304c42cdb452..a0d124fc94fd7cf945bf48e065d42f0ebbcf86f0
--- 1/httpx/dispatch/connection.py
--- 2/httpx/dispatch/connection.py
+++ b/httpx/dispatch/connection.py
@@@ -1,8 -1,7 +1,8 @@@
  import functools
  import typing
 +import ssl
  
- from ..concurrency import AsyncioBackend
+ from ..concurrency.asyncio import AsyncioBackend
  from ..config import (
      DEFAULT_TIMEOUT_CONFIG,
      CertTypes,

diff --cc httpx/dispatch/connection_pool.py
Simple merge