Depend on pyudev during runtime

In v2.1.fb60 an unconditional dependency to pyudev was added,
which needs to be specified in the egg info, otherwise pip install might fail with e.g.

File "local/lib/python2.7/site-packages/rtslib/utils.py", line 30, in <module>
     import pyudev
 ImportError: No module named pyudev

1 files changed, 1 insertions, 0 deletions

diff --git a/setup.py b/setup.py
index 48f6282..7770032 100755
--- a/setup.py
+++ b/setup.py
@@ -28,6 +28,7 @@ setup (
     url = 'http://github.com/open-iscsi/rtslib-fb',
     packages = ['rtslib_fb', 'rtslib'],
     scripts = ['scripts/targetctl'],
+    install_requires = ['pyudev >= 0.16.1'],
     classifiers = [
         "Programming Language :: Python",
         "Programming Language :: Python :: 3",