upgrade code base to Django 1.7, which is released in  2014-09-02
upgrade code base to Django 1.7, which is released in  2014-09-02
turn on the middleware to use memcached
turn off memcached, and use cacheops for caching
let Redis to cache all
use persisten connection
remove related field in Source model. Query performance improved
remove related field in Source model, and migrate it. Query performance improved
update README.md & TODO.md