Add requirements section to README.md
Add requirements section to README.md

- Pointing to composer.json

gartner/zf-apigility-admin,guliano/zf-apigility-admin,gartner/zf-apigility-admin,jguittard/zf-apigility-admin,ildanno/zf-apigility-admin,guliano/zf-apigility-admin,jguittard/zf-apigility-admin,ildanno/zf-apigility-admin