fixes an issue with reading session data, and adds some tests

fixes an issue with a missing ` in the code, which caused destroy fun…

…ction to return false/fail. Also tweaks to formatting.

Update README.md

* Making the class final with private attributes.

* Fixed an issue with the read()

* Making my changes that I found were necessary to get it working wit…

…h plain PHP.

* Altering authorship info to add myself.
* Changing package naming so I can publish this modified version.

Update SessionHandler.php

Ensure we store data in correct columns