WordPress Plugin: Notification [Simplified]

Project Description:
You must read the attached text file before bidding. This project is reposted because the previous contractor did not finish the job. In the interest of controlling budget and time, the functions of this plugin has been reduced and simplified.

=== [ WordPress Notification / Message Plugin ] ===

[ Caution ]

Regarding testing, before you hand over the demo for us to test, you must make sure you've done test yourself and no major problems can be found. You'll need to setup server for demo and testing. We won't provide our site for this purpose. If you deliver a half baked project to us, and we discovered major problems, we may deduct fees from the project for testing, in which case you will not receive the total amount.

[ Overview ]

This task involves creating a WordPress 3.5.1 plugin that provides notification capabilities, similar to freelancer.com or stackoverflow.com. The plugin only requires bare bone notification functions (sending, displaying, marking as read, database storage). The functions should be accessible from other plugins (later on, this project will be integrated into the system with other plugins). There is no requirement on front-end representation (page style), which means you can use the simplest possible page style. Please do not use complicated page styles even if they look good. We wanted something simple to integrate with.