Started using composer.
Replaced autoloader function in functions.php with built-in Composer autoloader.
Added Pimple as a project dependency to tidy up class constructors.
Choosing to gitignore all files in Vendor directory as unnecessary. That's what composer is for after all.
Changed readme to include mention of composer/pimple
Added 'vendor' directory in to version control. Stops the installation of composer being a requirement to use the project. 
Added the User class in to Pimple and updated the User creation in Quiz().
Removed concrete DB instantiation from classes and placed in Pimple