Remove old unsupported Symfony versions

Author: Cliff Odijk

.travis.yml

@@ -15,12 +15,8 @@ matrix:
       env: COMPOSER_FLAGS="--prefer-lowest"
 
     # Test Symfony versions
-    - php: 7.2
-      env: SYMFONY_VERSION=2.7.*
     - php: 7.2
       env: SYMFONY_VERSION=2.8.*
-    - php: 7.2
-      env: SYMFONY_VERSION=3.3.*
     - php: 7.2
       env: SYMFONY_VERSION=3.4.*
     - php: 7.2