Bump python-savannaclient version to >= 0.4.0

It includes support for all features that'll be released in i1.

Change-Id: I7809389b4e1332ecc4e8a7122819b7411d8662cf
Allow Django 1.5 and 1.6

Prerequirement for https://review.openstack.org/#/c/58561/

Change-Id: I6b71d6e45b14a8c40ba7b3f82e8b0f7846e61ebe
Merge "Bump python-savannaclient version to >= 0.4.0"