Create DebugBar class (issue #8)

This version introduces multiple enhancements:

added base class to start and handle debugbar
some example changes and degubgar usage
fixed composer

Details of additions/deletions below:
--------------------------------------------------------------

Added:      Debug/Assets/dark.css
            -- Added --
                change some visual elements of debugbar

Added:      examples/debugbar.php
            -- Added --
                example of extended debugbar usage

Added:      Debug/DebugBar.php
            -- Added --
                extends some debugbar functionality

Modified:   composer.json
            -- Updated --
                fixed namespace for PSR-4

Modified:   examples/header.php
            -- Added --
                include debugbar header