fix reading version from _version.py

setup.py

@@ -4,9 +4,13 @@
 # Copyright (c) Viacheslav Ostroukh
 # Distributed under terms of 2-clause BSD license
 
-from os.path import exists
+from os.path import exists, join
 from setuptools import setup
 
+
+with open(join('nb_slurm', '_version.py')) as version:
+    exec(version.read())
+
 install_requires = [
     'jupyter_client',
     'traitlets',
@@ -15,7 +19,7 @@ install_requires = [
 ]
 
 setup(name='nb_slurm',
-      version='0.0.0',
+      version=__version__,
       description='Kernel manager for Jupyter for launching kernels via SLURM',
       url='https://gitlab.com/slavoutich/nb_slurm',
       maintainer='Viacheslav Ostroukh',