Merge pull request #38 from sureshvtt/master

Created ajax view for getting rank
Merge pull request #39 from sureshvtt/master

Removed topic nav tab from performance.html
Done celery ranking and pagination in ranklist
Merge branch 'master' of https://github.com/redrosevishnu/pscexams
Added group study nitification code
Now free user can access only 2 tests for each subtopic