bdist_rpm does not build an RPM

[gcoxmoz]

Running python setup.py bdist_rpm bombs out:

+ python setup.py build
Traceback (most recent call last):
  File "setup.py", line 17, in <module>
    with open(requirements_dev_filename) as fd:
IOError: [Errno 2] No such file or directory: '/home/me/VPN/duo_client_python/build/bdist.linux-x86_64/rpm/BUILD/duo_client-3.1.0/requirements-dev.txt'
error: Bad exit status from /var/tmp/rpm-tmp.ZZiQil (%build)

I think the simple fix is to add requirements-dev.txt to MANIFEST.in, but perhaps there's a different way that fits with why there's a dev file to begin with.

[xdesai]

Fix landed.
Thanks for finding the issue!