Fix setup.py to work with Python 2.7

Author: althonos

setup.py

@@ -1,4 +1,9 @@
 #!/usr/bin/env python
 
+import os
+
+with open(os.path.join("fs", "_version.py")) as f:
+    exec(f.read())
+
 from setuptools import setup
-setup()
+setup(version=__version__)