Put long_description in setup.cfg.

I hope this fixes a UnicodeDecodeError on Python 3.6 on some machines,
without needing special code in setup.py.

setup.cfg

@@ -1,3 +1,6 @@
+[metadata]
+long_description = file: README.rst, CHANGES.rst
+
 [zest.releaser]
 create-wheel = yes
 

setup.py

@@ -3,33 +3,12 @@
 version = '2.0.3.dev0'
 
 
-def read(filename):
-    with open(filename) as myfile:
-        try:
-            return myfile.read()
-        except UnicodeDecodeError:
-            # Happens on one Jenkins node on Python 3.6,
-            # so maybe it happens for users too.
-            pass
-    # Opening and reading as text failed, so retry opening as bytes.
-    with open(filename, "rb") as myfile:
-        contents = myfile.read()
-        return contents.decode("utf-8")
-
-
-long_description = "\n".join(
-    [
-        read("README.rst"),
-        read("CHANGES.rst"),
-    ]
-)
-
-
 setup(
     name='Products.CMFPlacefulWorkflow',
     version=version,
     description="Workflow policies for Plone",
-    long_description=long_description,
+    # Note: long_description is in setup.cfg
+    # to avoid needing workarounds for UnicodeDecodeErrors.
     classifiers=[
         "Development Status :: 5 - Production/Stable",
         "Framework :: Plone",