node: postgresql/ 디렉토리 변경
    modified:   README.md
    new file:   xml/README.md
    renamed:    composition.xml -> xml/composition.xml
    renamed:    create-db.js -> xml/create-db.js
    renamed:    drop-db.js -> xml/drop-db.js
    renamed:    insert-data.js -> xml/insert-data.js