Merge pull request #51 from cs198/fix-comments-backend

Fix comments backend
Fix submission uploading. It works on single files, multiple files, and when files are removed after selection.
Merge pull request #53 from cs198/fix-submissions-controller

Fix submission uploading. It works on single files, multiple files, and ...
Cleaned up FileUploaderCtrl.js
Cleaned up submissions_controller to allow valid submissions to show up even if invalid submissions (i.e. person_id = 1) are present