RelNode: updated PHPDoc comments

Signed-off-by: Jan Pecha <janpecha@email.cz>
source code moved into /src directory

Signed-off-by: Jan Pecha <janpecha@email.cz>
added composer.json

Signed-off-by: Jan Pecha <janpecha@email.cz>
changed namespace Cz\RelNode => Cz

Signed-off-by: Jan Pecha <janpecha@email.cz>
bug fix - $dir is NULL default

Signed-off-by: Jan Pecha <janpecha@email.cz>
Tests: first tests

Signed-off-by: Jan Pecha <janpecha@email.cz>
changed recognizing of root

Signed-off-by: Jan Pecha <janpecha@email.cz>
added readme

Signed-off-by: Jan Pecha <janpecha@email.cz>