add isort config

Author: tony

setup.cfg

@@ -1,3 +1,15 @@
 [flake8]
 exclude = .*/,.tox,*.egg,libtmux/_compat.py,libtmux/__*__.py
 select = E,W,F,N
+
+[isort]
+combine_as_imports= true
+default_section = THIRDPARTY
+include_trailing_comma = true
+multi_line_output = 3
+known_pytest = pytest,py
+known_first_party = libtmux
+split_before_closing_bracket = true
+sections = FUTURE,STDLIB,PYTEST,THIRDPARTY,FIRSTPARTY,LOCALFOLDER
+line_length = 79
+not_skip = __init__.py