Added release notes for 0.13.0
Added release notes for 0.13.0

Change-Id: I51374661a5ce58cd2a970a75893b1251ab6e176b

klmitch/python-glanceclient,alexpilotti/python-glanceclient,varunarya10/python-glanceclient,JioCloud/python-glanceclient,openstack/python-glanceclient,varunarya10/python-glanceclient,mmasaki/python-glanceclient,JioCloud/python-glanceclient,openstack/python-glanceclient,mmasaki/python-glanceclient,klmitch/python-glanceclient,alexpilotti/python-glanceclient