Fixes tests, adds PHP 7.3 (#257)

Author: bshaffer

.travis.yml

@@ -1,19 +1,22 @@
 language: php
 
 php:
-  - 5.4
-  - 5.5
   - 5.6
   - 7.0
   - 7.1
   - 7.2
+  - 7.3
 
 matrix:
   include:
     - php: 5.3
       dist: precise
+    - php: 5.4
+      dist: trusty
+    - php: 5.5
+      dist: trusty
 
 sudo: false
 
 before_script: composer install
-script: phpunit
+script: vendor/bin/phpunit

composer.json

@@ -24,6 +24,6 @@
         }
     },
     "require-dev": {
-        "phpunit/phpunit": " 4.8.35"
+        "phpunit/phpunit": "^4.8|^5"
     }
 }