fix python 2 compat

fix #138

Author: noraj

setup.py

@@ -1,8 +1,13 @@
 # -*- coding: utf-8 -*-
 from distutils.core import setup
+import sys
 
-with open("README.rst", encoding="utf-8") as rfile:
-    long_description = rfile.read()
+if sys.version_info >= (3,0):
+    with open("README.rst", encoding="utf-8") as rfile:
+        long_description = rfile.read()
+else: # encoding not compatible with python2
+    with open("README.rst") as rfile:
+        long_description = rfile.read()
 
 setup(
     name="python-libnmap",