Update composer packages

src/composer.json

@@ -1,15 +1,16 @@
 {
     "require": {
-        "slim/slim": "^3.0",
+        "slim/slim": "^4.9",
         "ezyang/htmlpurifier": "^4.9",
         "phpmailer/phpmailer": "^6.0",
         "erusev/parsedown": "^1.6",
-        "slim/twig-view": "^2.2",
-        "knplabs/github-api": "^2.5",
-        "php-http/guzzle6-adapter": "^1.1",
-        "cache/filesystem-adapter": "^1.0",
-        "monolog/monolog": "^1.23",
-        "evert/sitemap-php": "^1.2"
+        "slim/twig-view": "^3.3.0",
+        "knplabs/github-api": "^3.5",
+        "php-http/guzzle7-adapter": "^1.0",
+        "cache/filesystem-adapter": "^1.2",
+        "monolog/monolog": "^2.3",
+        "evert/sitemap-php": "^1.2",
+        "php-di/php-di": "^6.3"
     },
     "autoload":{
         "psr-0":{