Update djangosaml dependency

Using version 0.17.1 which depends on pysaml 4.5.0, what doesnt have the vulnerability. Add an option to saml sp, to not require signed response.

circle/circle/settings/base.py

@@ -495,6 +495,7 @@ if get_env_variable('DJANGO_SAML', 'FALSE') == 'TRUE':
                 },
                 'required_attributes': required_attrs,
                 'optional_attributes': optional_attrs,
+                'want_response_signed': False,
             },
         },
         'metadata': {'local': [remote_metadata], },

requirements/base.txt

@@ -16,7 +16,7 @@ django-sizefield==0.9.1
 django-statici18n==1.4.0
 django-tables2==1.10.0
 django-taggit==0.22.1
-djangosaml2==0.16.10
+djangosaml2==0.17.1
 git+https://git.ik.bme.hu/circle/django-sshkey.git
 docutils==0.12
 Jinja2==2.7.3