Expose isort preferences for tools. (home-assistant#4481)

* Expose isort preferences for tools.

* Adhere to pylints sorted imports requirement.

* More documentation, set typing in between stdlib and 3rd party.

homeassistant/util/async.py

@@ -6,6 +6,7 @@
 from asyncio.futures import Future
 
 try:
+    # pylint: disable=ungrouped-imports
     from asyncio import ensure_future
 except ImportError:
     # Python 3.4.3 and earlier has this as async

setup.cfg

@@ -10,3 +10,17 @@ exclude = .venv,.git,.tox,docs,www_static,venv,bin,lib,deps,build
 
 [pydocstyle]
 match_dir = ^((?!\.|www_static).)*$
+
+[isort]
+# https://github.com/timothycrosley/isort
+# https://github.com/timothycrosley/isort/wiki/isort-Settings
+# splits long import on multiple lines indented by 4 spaces
+multi_line_output = 4
+indent = "    "
+# by default isort don't check module indexes
+not_skip = __init__.py
+# will group `import x` and `from x import` of the same module.
+force_sort_within_sections = true
+# typing is stdlib on py35 but 3rd party on py34, let it hang in between
+known_inbetweens = typing
+sections = FUTURE,STDLIB,INBETWEENS,THIRDPARTY,FIRSTPARTY,LOCALFOLDER