Update README.md

/ - the root of the application (not necessarily the server's web root)
/bin - all my data processing scripts
/img - images and PHP scripts that produced images would go here
/inc - include files; only config scripts would be in the root of this subdirectory
/inc/classes - my class files (one class per file)
/inc/func - function files, grouped by type (i.e. similar functions in one file)
/template - my template files