Merge pull request #22 from pigmike/master

Permission Module
fix create exam error
Merge pull request #23 from hutuxiansheng/master

fix exam create error
fix publish exam
Merge pull request #24 from hutuxiansheng/master

fix exam publish error
Add discuss routes for create new discuss.
add deal paper in background
meger jasli2 master branch
Add discuss controller.
change style for attachment list.
add some permission to view course class information.
adjust training plan views.
1. Adjust comment controller to let comment act as polymorphic.
2. Adjust training plan views.
submit paper to teacher
Adjust admin dashboard view.
add student result for examination
In user's dashboard. Showing TODO list and trace project as the most inportant information.
Also add action direct in TODO and trace project to let use handle more easily.
Remove debug information.
Adjust view to display cousre and class. Add examination link.
Add course class publish address and time feature and sent out notification to students.