Merge pull request #168 from rbpisupati/without_numpy

import error of sys when numpy is not present

setup.py

@@ -2,7 +2,7 @@
 from __future__ import absolute_import, print_function, division
 from ast import literal_eval
 from setuptools import setup, Extension, find_packages
-
+import sys
 
 DISTNAME = 'scikit-allel'