adding logo

Author: Julien Neuhart

README.md

@@ -1,3 +1,7 @@
+<p align="center">
+<img src="./logo.png" alt="kickoff-docker-php logo" />
+</p>
+
 [![PHP 7.1](https://img.shields.io/badge/PHP-7.1-green.svg)](apache/Dockerfile#L1)
 [![Composer latest](https://img.shields.io/badge/Composer-latest-green.svg)](apache/Dockerfile#6)
 [![MySQL 5.7](https://img.shields.io/badge/MySQL-5.7-green.svg)](docker-compose.yml.template#L23)