Bump eventlet to 0.12.0

This version has important fixes required
for ZeroMQ (spurious wakeups).

Fixes bug 1065532.

Change-Id: I16b9220db1f5bf16a24644887963ce18e4e5ecbd
Use oslo-config-2013.1b3

The cfg API is now available via the oslo-config library, so switch to
it and remove the copied-and-pasted version.

Add the 2013.1b3 tarball to tools/pip-requires - this will be changed
to 'oslo-config>=2013.1' when oslo-config is published to pypi. This
will happen in time for grizzly final.

Remove the 'deps = pep8==1.3.3' and 'deps = pyflakes' from tox.ini as
it means all the other deps get installed with easy_install which can't
install oslo-config from the URL.

Change-Id: I4815aeb8a9341a31a250e920157f15ee15cfc5bc
Merge "Bump eventlet to 0.12.0"