updated upgrading docs for Django 1.11
updated upgrading docs for Django 1.11

yan99uic/django-DefectDojo,OWASP/django-DefectDojo,rackerlabs/django-DefectDojo,rackerlabs/django-DefectDojo,grendel513/django-DefectDojo,OWASP/django-DefectDojo,rackerlabs/django-DefectDojo,OWASP/django-DefectDojo,yan99uic/django-DefectDojo,grendel513/django-DefectDojo,OWASP/django-DefectDojo,yan99uic/django-DefectDojo,grendel513/django-DefectDojo,rackerlabs/django-DefectDojo,yan99uic/django-DefectDojo,OWASP/django-DefectDojo,grendel513/django-DefectDojo