Add Werkzeug>=0.7 to global-requirements.txt

Werkzeug>=0.7 is a direct dependency of Designate, and a transitive
dependency of the Flask WSGI framework used by Designate and
Ceilometer.

Werkzeug is a stable + actively maintained collection of WSGI
utilities, providing the basis for the Flask WSGI framework. The
codebase supports Python 2.6, 2.7 and 3.3, is licenced under
the BSD licnese, and is packaged on Ubuntu, Debian, Fedora.

Change-Id: I955dc03010c9988f0dc989217c5c084eede34fb5
Merge "Add Werkzeug>=0.7 to global-requirements.txt"