Enable newer PHP versions on Travis

Author: SilverFire

.travis.yml

@@ -4,6 +4,10 @@ php:
   - 7.0
   - 7.1
   - 7.2
+  - 7.3
+  - 7.4
+  - 8.0
+  - 8.1
 
 before_script:
   - composer install -n --dev --prefer-source