added markdown and djangorestframework to install requirements
added rest_framework and api apps to INSTALLED_APPS
added the api routing URL
added the GradeSerializer
added the Grade API view
routed the GradeViewSet to '/api/grades'
__init__ to __win_it__
only admins should be able to see grades
added the login/logout urls to the browsable API
Merge pull request #155 from qdonnellan/develop

grade api is operational!