Raise Babel requirements to >= 1.3

1.1 is the first version that installs properly with Pip 1.4,
which we require already. Furthermore Keystone now added
a dependency on a newer Babel.

However, 1.1 has a bug so that babel won't compile the zh_CN locale, so
we have to update to the 1.3 version which fixes that bug.

http://babel.pocoo.org/docs/changelog/#version-1-3

Related-Bug: 1232235
Related-Bug: 1233694

Change-Id: I4060a0ca83f82e89c6d5b3e97bafb60e09db542b
Merge "Raise Babel requirements to >= 1.3"