Updated openstack/openstack
Project: openstack/swift  f3f437ffb984fd008faeb309e4d2cfee96ffb770
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Updates tox.ini to use new features

tox 1.6 allows us to skip the sdist step, which is slow. This does that.
It also allows us to override the install line. In this case, it's
important as it allows us to stop getting pre-release software we
weren't asking for.

Original patch by Monty Taylor, talked about here:
http://lists.openstack.org/pipermail/openstack-dev/2013-September/015495.html

Change-Id: I2042cae5ebf5467408fe6cdb71f6147081b72ca6