Import fixes for S3 configuration (#57)
Import fixes for S3 configuration (#57)

* Challenges models modified to fix circular import

* Hosts model modified to fix circulr import

* Sample urlpattern added to all apps

* Migrations added to gitignore

* Storage path fixed for storing media and static files on production server

* Import fixes

* PEP8 fixes

taranjeet/EvalAI,taranjeet/EvalAI,taranjeet/EvalAI,taranjeet/EvalAI