Move flake8 config to setup.cfg.

.flake8

@@ -1,5 +0,0 @@
-[flake8]
-ignore = W503
-max-line-length = 89
-max-complexity = 10
-select = B,C,E,F,W,T4,B9

setup.cfg

@@ -57,3 +57,9 @@ exclude =
     images*
     scripts*
     tests*
+
+[flake8]
+ignore = W503
+max-line-length = 89
+max-complexity = 10
+select = B,C,E,F,W,T4,B9