Support symfony 4 and 5 (#8)

* Add support for symfony/console 4 and 5

* Update source link to point to the right repository

* Bump minimum PHP requirement to 5.6

* Replace abandoned coverage package with friends-of-phpspec/phpspec-code-coverage

composer.json

@@ -14,27 +14,27 @@
         },
         {
             "name": "Community contributors",
-            "homepage": "https://github.com/portphp/symfony-console-adapter/graphs/contributors"
+            "homepage": "https://github.com/portphp/symfony-console/graphs/contributors"
         }
     ],
     "support": {
         "issues": "https://github.com/portphp/portphp/issues",
-        "source": "https://github.com/portphp/symfony-console-adapter",
+        "source": "https://github.com/portphp/symfony-console",
         "docs": "https://portphp.readthedocs.org"
     },
     "require": {
-        "php": ">=5.4.0",
-        "portphp/portphp": "^1.0.0",
-        "symfony/console": "^2.7 || ^3.0"
+        "php": "^5.6 || ^7.0",
+        "portphp/portphp": "^1.1",
+        "symfony/console": "^2.7 || ^3.0 || ^4.0 || ^5.0"
     },
     "autoload": {
         "psr-4": {
             "Port\\SymfonyConsole\\": "src/"
         }
     },
     "require-dev": {
-        "phpspec/phpspec": "^2.1",
-        "henrikbjorn/phpspec-code-coverage" : "^1.0"
+        "phpspec/phpspec": "^3.0",
+        "friends-of-phpspec/phpspec-code-coverage" : "^3.0"
     },
     "extra": {
         "branch-alias": {