fixing markdown in order to display correct chapters (#2)

Updated readme with all five approaches + plus one bonus one

Added examples with Nested Sets and Materialized path.

Updated with combination Nested sets + parent reference.

Added picture for Materialized path

Nested sets pictures

Finished with nexted sets moving example

Nested Sets examples

Added illustration for nexted sets

Continued working with nexted sets

Started with Materialized Path approach and Nested Sets

Started working with nested sets demo

last changes to readme

Mentioned indexes

Demo changes.