Add initial support for PHP7 (#97)

* Add initial support for PHP7

* Update PHP env with now an PSR3 logger (Monolog). Now you can also create a handler function with PSR7 Http message and PSR3 logger in parameter.

* Add examples for PHP7 environement

* For development you can create a function in this path /app/userfuncdev.php it will be loaded

* Switch to alpine base image

* handler now receive an array with request, response and logger object

environments/php7/index.php

@@ -0,0 +1,4 @@
+<?php
+require __DIR__ . '/vendor/autoload.php';
+$server = new PHPEnv\Server();
+$server->run();