Travis: add PHP 7.3, 7.4

Author: f3l1x

.travis.yml

@@ -2,6 +2,8 @@ language: php
 php:
 - 7.1
 - 7.2
+- 7.3
+- 7.4
 
 before_install:
 # turn off XDebug
@@ -18,20 +20,20 @@ script:
 jobs:
   include:
   - stage: Quality Assurance
-    php: 7.1
+    php: 7.4
     script:
     - composer run-script qa
 
   - stage: Test Coverage
-    php: 7.1
+    php: 7.4
     script:
     - composer run-script coverage
     after_script:
     - wget https://github.com/satooshi/php-coveralls/releases/download/v1.0.1/coveralls.phar
     - php coveralls.phar --verbose --config tests/.coveralls.yml
 
   - stage: Phpstan
-    php: 7.1
+    php: 7.4
     script:
     - composer run-script phpstan-install
     - composer run-script phpstan
@@ -48,4 +50,4 @@ sudo: false
 
 cache:
   directories:
-  - $HOME/.composer/cache
+  - $HOME/.composer/cache