Adds a users application. Adds authentication process and limits some views (calculate) to authenticated users.
Added MIT license
Added authors on copyright file. I hope I got them all right. Correct me if I'm wrong.
Merge pull request #31 from rasilang/userauth

Adds user authentication within the site.
Replaces the old zipfile in /media/uploads with the newly uploaded file with the same filename.
Replaces the old zipfile in /media/uploads with the newly uploaded file with the same filename.
Merge branch 'overwritefile'