Using a consistent open at setup.py

setup.py

@@ -7,16 +7,17 @@
     from setuptools import setup
 except ImportError:
     from distutils.core import setup
+from codecs import open
 
 
-with open('README.rst') as readme_file:
-    readme = readme_file.read()
+with open('README.rst', encoding='utf-8') as f:
+    readme = f.read()
 
-with open('HISTORY.rst') as history_file:
-    history = history_file.read().replace('.. :changelog:', '')
+with open('HISTORY.rst', encoding='utf-8') as f:
+    history = f.read().replace('.. :changelog:', '')
 
-with open('requirements.txt') as requirements_file:
-    requirements = requirements_file.read()
+with open('requirements.txt', encoding='utf-8') as f:
+    requirements = f.read()
 
 setup(
     name='seabird',