Fixes #6085. (#6091)

The value of norecusedirs is the default in newer versions of pytest which is
listed at
https://docs.pytest.org/en/3.0.0/customize.html#confval-norecursedirs.

acme/MANIFEST.in

@@ -1,5 +1,6 @@
 include LICENSE.txt
 include README.rst
+include pytest.ini
 recursive-include docs *
 recursive-include examples *
 recursive-include acme/testdata *

acme/pytest.ini

@@ -0,0 +1,2 @@
+[pytest]
+norecursedirs = .* build dist CVS _darcs {arch} *.egg