TravisCI tests up to PHP 7.4 (#74)

* Update .travis.yml

* Update composer.json

* Update .travis.yml

Author: mondrake

.travis.yml

@@ -5,19 +5,22 @@ env:
   - PREFER_LOWEST=""
 
 php:
-    - 5.4
-    - 5.5
     - 5.6
     - 7.0
     - 7.1
     - 7.2
+    - 7.3
+    - 7.4
     - nightly
-    - hhvm
 
 matrix:
+  include:
+    - php: 5.4
+      dist: trusty
+    - php: 5.5
+      dist: trusty
   allow_failures:
     - php: nightly
-    - php: hhvm
   fast_finish: true
 
 before_script:

composer.json

@@ -19,6 +19,6 @@
       "bin-dir": "bin"
     },
     "require-dev": {
-        "phpunit/phpunit": "^4.8.35 || 5.* || 6.*"
+        "phpunit/phpunit": "^4.8.35 || ^5 || ^6 || ^7"
     }
 }