Use explicit UTF8 encoding (#452)

* Use explicit UTF8 encoding

Resolves #451

* Resolve encoding issue with Python3 (#1)

* Use open from Py3 in Py2

setup.py

@@ -4,6 +4,7 @@
 .. _github: https://www.github.com/snide/sphinx_rtd_theme
 
 """
+from io import open
 from setuptools import setup
 from sphinx_rtd_theme import __version__
 
@@ -16,7 +17,7 @@
     author='Dave Snider',
     author_email='dave.snider@gmail.com',
     description='Read the Docs theme for Sphinx',
-    long_description=open('README.rst').read(),
+    long_description=open('README.rst', encoding='utf-8').read(),
     zip_safe=False,
     packages=['sphinx_rtd_theme'],
     package_data={'sphinx_rtd_theme': [