Add PHP 7.1 to travis

.travis.yml

@@ -1,15 +1,26 @@
+sudo: required
+
 language: php
 
+# Stage order
+stages:
+  - pre-conditions
+  - test
+  - quality
+
 php:
+  - 7.1
   - 7.2
   - 7.3
+  - 7.4
 
-matrix:
-  fast_finish: true
+
+env:
+  - COMMAND="composer install"
+  - COMMAND="composer update"
 
 before_script:
-  - if [[ "$TRAVIS_PHP_VERSION" == "7.2" ]]; then composer require php-coveralls/php-coveralls; fi
-  - if [[ "$TRAVIS_PHP_VERSION" == "7.3" ]]; then composer require --dev vimeo/psalm; fi
+  - ${COMMAND}
 
 script:
   - php vendor/bin/phpunit --no-coverage
@@ -33,6 +44,14 @@ jobs:
     #  Pre-conditions stage  #
     ##########################
 
+    - stage: pre-conditions
+      env: Syntax check PHP
+      php: 7.1
+      before_script:
+        - composer install
+      script:
+        - vendor/bin/check-syntax-php.sh
+
     - stage: pre-conditions
       env: Syntax check PHP
       php: 7.2