Pin Babel to <1.0 since it doesn't play well with pip 1.4

The latest Babel, 1.0, adds a dependency on
pytz. Further, pytz uses date-based versioning which is not
supported by default in the newest pip, 1.4. Adding a fake direct
dependency on pytz with a minimum declared version before installing
Babel works around this issue.

Fixes bug 1205546

Change-Id: Ie52dd85eac595ba8ee35e3342130648010246943