update all dependencies and php8 in travis

.travis.yml

@@ -2,6 +2,7 @@ language: php
 php:
   - '7.1'
   - '7.2'
+  - '8.0'
 
 install:
   - composer install

composer.json

@@ -14,12 +14,12 @@
   "require": {
     "php": "^7.1.3 | ^8.0",
     "monolog/monolog": "~1.11 | ^2.0",
-    "symfony/console": "^4.0",
+    "symfony/console": "^4.0 | ^5.0",
     "symfony/filesystem": "^4.0 | ^5.0",
-    "symfony/event-dispatcher": "^4.0",
+    "symfony/event-dispatcher": "^4.0 | ^5.0",
     "symfony/finder": "^4.0 | ^5.0",
-    "symfony/yaml": "^4.0",
-    "symfony/process": "^4.0"
+    "symfony/yaml": "^4.0 | ^5.0",
+    "symfony/process": "^4.0 | ^5.0"
   },
   "require-dev": {
     "phpunit/phpunit": "^8.0",