[buildout] Fix minium versions for DRF and DRF swagger

Otherwise the version from the CI are used and are too old

buildout.cfg

@@ -17,7 +17,9 @@ versions = versions
 
 [versions]
 django = >=1.11,<2.0
+django-rest-swagger = >2.1
 django-guardian = >=1.3
+djangorestframework = >3.7
 django-activity-stream = >= 0.6.0
 
 [sysegg]