v0.3.0

• Fix bug in request url for upload file
• Fix bug in update actions of course and user
• Remove folder_name column from courses and users
• Remove paperclip related columns and code from outcome_files
• Remove paperclip related columns and code from users
• Remove paperclip related columns and code from courses
• Drop snippet_files table and related code
• Fix path for shrine file in terms of relative_url
• Fix data type for *_data of shrine
• Create outcome_file.upload_data for shrine
• Snippet image_data instead of SnippetFile.upload for shrine
• Create user and course image_data for shrine
• Use shrine gem for course & user image