Add compatibility informations

Add to section the compatibility informations
Add unit test for Compatibility Section
Revert Allowing Section References to be Non-Numeric

A change was made when adding in the Compatability comments to allow
section references to be non-numeric. More work needs to be done to
allow for proper sorting of non-numeric section references before this
change can be released to the public.

Fixes a fix code style errors.
Updates from PSR-0 to PSR-4

Changes the autoloader from using PSR-0 to PSR-4 to make the lib
directory shallower.