Update setup.py

fix `UnicodeDecodeError: 'gbk' codec can't decode byte 0x88 in position 16820: illegal multibyte sequence` when install

Author: Daic115

setup.py

@@ -9,7 +9,7 @@
 def main():
     """Cloudflare API code - setup.py file"""
 
-    with open('README.md') as read_me:
+    with open('README.md', encoding="utf-8") as read_me:
         long_description = read_me.read()
 
     with open('CloudFlare/__init__.py', 'r') as f: