use recommended format for configuration

JoelBender · JoelBender · commit c30730b4355d · 2016-08-23T16:14:40.000-04:00
diff --git a/setup.cfg b/setup.cfg
@@ -5,7 +5,7 @@ ignore = E123,E221,E226,E302,E41,E701
 max-line-length = 160
 max-complexity = 10
 
-[pytest]
+[tool:pytest]
 
 [aliases]
 test=pytest
