Home-brewed file upload in Ruby on Rails

Most of this comes from others' work, but I was able to tool it to my needs and fix some bugs. All of these lines go in the model, which for me has a :file and :content_type attributes. :file stores the complete path to the uploaded file. Be sure to change the String in path_to_file to the place where you want files stored, and that proper permissions are set on that path. Also, sanitize_filename doesn't HAVE to be a private method -- make it public if you want.

Fixed some bugs.