MarkUsProject/Markus — pull request #1648 by zhangsu (2014-08-02 02:22:40+00:00)
Title: Avoid n+1 queries when downloading all submissions

Lots of queries are redundant in the logic of downloading all
submissions and can be avoided by eagerly loading the associations.

This deals with #1484.

Tested:
- rspec
- rake test:units
- rake test:functionals