drop travis.yml build - no longer used - see #836

.travis.yml

@@ -1,33 +0,0 @@
-language: php
-php:
-  - 7.2
-  - 7.3
-  - 7.4
-  - 8.0
-
-services:
-  - mysql
-  - postgresql
-
-cache:
-  directories:
-    - $HOME/.composer/cache
-    - $HOME/vendor
-
-before_install:
-  - mysql -e 'CREATE DATABASE postfixadmin;'
-  - psql -c 'create database postfixadmin;' -U postgres
-
-
-before_script:
-  - travis_retry composer install --no-interaction --prefer-source --dev
-  - mkdir -p build/logs
-
-script:
-  - composer build
-  - DATABASE=sqlite vendor/bin/phpunit tests/
-  - DATABASE=mysql vendor/bin/phpunit --coverage-clover=build/logs/clover.xml tests/
-  - DATABASE=postgresql vendor/bin/phpunit tests/
-
-after_success: 
-  - travis_retry php vendor/bin/php-coveralls