Fix possible decoding problem when locale is set to C/ASCII

Author: Josue

setup.py

@@ -5,7 +5,7 @@
 
 import materializecssform
 
-with open("README.md", "r") as fh:
+with open("README.md", "r", encoding="utf-8") as fh:
     long_description = fh.read()
 
 setup(