Bump Babel requirement to >=1.0

The Zuul client uses babel.dates.format_timedelta which was introduced
with 1.0 http://babel.pocoo.org/docs/changelog/#version-1-0

Ubuntu Precise has 0.9.6 causing the Zuul client to abort because of the
missing method.

Change-Id: I60ed0d61c97091c17a926770ed1a02f1156ec5e0
Merge "Bump Babel requirement to >=1.0"