Merge pull request #17 from edx/will/upgrade-django-extensions

Upgrade django-extensions to 1.5.5

requirements.txt

 dogapi==1.2.1
 django>=1.4,<1.5
-django-extensions==1.2.5
+django-extensions==1.5.5
 django-model-utils==1.4.0
 djangorestframework<2.4
 pytz==2012h