Run tests on PHP 7.4 and simplify test matrix

Author: SimonFrings

.travis.yml

@@ -1,19 +1,18 @@
 language: php
 
-php:
-  - 5.4
-  - 5.5
-  - 5.6
-  - 7.0
-  - 7.1
-  - 7.2
-  - 7.3
-
 # lock distro so new future defaults will not break the build
 dist: trusty
 
 matrix:
   include:
+    - php: 5.4
+    - php: 5.5
+    - php: 5.6
+    - php: 7.0
+    - php: 7.1
+    - php: 7.2
+    - php: 7.3
+    - php: 7.4
     - name: "Windows"
       os: windows
       language: shell # no built-in php support