Feature: Use AWS for File Storage

[Wineshuga]

Description

In this branch, I made the following changes or modifications:

• I created an S3 bucket on AWS and added it to the applications storage.yml file.
• I added the AWS access keys to the credential.yml file
• I changed the active storage service in the development.rb and the production.rb files to use Amazon
• I updated the category model to have an attachment called image and used the attachment in the form field
• I fixed the style issue on the add buttons on the category and transaction index pages