fix setup error

setup.py

+#!/usr/bin/env python
+
 """Set up features."""
 from distutils.core import setup
 from os import path
@@ -8,7 +10,7 @@ def extract_version():
       with open(path.join('pydtnsim', '__init__.py')) as f:
             for line in f:
                   if line.startswith('__version__'):
-                        return line.split('"')[1]
+                        return line.split("'")[1]
 
 def extract_requirements():
       """Extract requirements function."""