Add test config for PHP 7.4

Author: ivanvermeyen

.travis.yml

@@ -1,4 +1,5 @@
 language: php
+dist: trusty
 
 matrix:
     include:
@@ -20,6 +21,14 @@ matrix:
           env: ILLUMINATE_VERSION=5.8.* TESTBENCH_VERSION=3.8.*
         - php: 7.3
           env: ILLUMINATE_VERSION=5.7.* TESTBENCH_VERSION=3.7.*
+        - php: 7.4
+          env: ILLUMINATE_VERSION=7.* TESTBENCH_VERSION=5.*
+        - php: 7.4
+          env: ILLUMINATE_VERSION=6.* TESTBENCH_VERSION=4.*
+        - php: 7.4
+          env: ILLUMINATE_VERSION=5.8.* TESTBENCH_VERSION=3.8.*
+        - php: 7.4
+          env: ILLUMINATE_VERSION=5.7.* TESTBENCH_VERSION=3.7.*
 
 before_script: