Add service_identity module
Add service_identity module

Squashes the following warning when starting Buildbot:

2015-10-22 19:41:50+0000 [-]
/usr/local/lib/python2.7/dist-packages/twisted/internet/_sslverify.py:184:
exceptions.UserWarning: You do not have the service_identity module installed.
Please install it from <https://pypi.python.org/pypi/service_identity>.
Without the service_identity module and a recent enough pyOpenSSL tosupport
it, Twisted can perform only rudimentary TLS client hostnameverification.
Many valid certificate/hostname mappings may be rejected.

setupminimal/saltfs,servo/saltfs,rwaweber/saltfs,UK992/saltfs,UK992/saltfs,setupminimal/saltfs,servo/saltfs,ALikhachev/saltfs,UK992/saltfs,ALikhachev/saltfs,ALikhachev/saltfs,rwaweber/saltfs,setupminimal/saltfs,rwaweber/saltfs