Merge pull request #27 from edx/ammar/dj18-update-django-extensions

update django-extensions

requirements.txt

 dogapi==1.2.1
-# disabled because django_extension is broken with django 1.8.6
-# https://github.com/django-extensions/django-extensions/issues/759
-# re-enable it once there is a new release availble for django-extensions 
-#django>=1.8,<1.9
-django==1.8.5
-django-extensions==1.5.5
+django>=1.8,<1.9
+django-extensions==1.5.9
 django-model-utils==2.3.1
 djangorestframework>=3.1,<3.2
 jsonfield==1.0.3