Add setuptools-git support

Standard way of generating tarballs across
the openstack project.

Change-Id: I9aede3008df212ff6b0191c2152137d131e96e4b
Signed-off-by: Chuck Short <chuck.short@canonical.com>

setup.py

@@ -31,6 +31,7 @@ setuptools.setup(
     packages=setuptools.find_packages(exclude=['bin']),
     include_package_data=True,
     test_suite='nose.collector',
+    setup_requires=['setuptools-git>=0.4'],
     scripts=['bin/ceilometer-agent-compute',
              'bin/ceilometer-agent-central',
              'bin/ceilometer-collector'],