Add php7.3 in travis tests

Author: magnetik

.travis.yml

@@ -5,6 +5,7 @@ language: php
 php:
   - 7.1
   - 7.2
+  - 7.3
 
 sudo: false
 
@@ -25,6 +26,8 @@ matrix:
       env: SYMFONY_VERSION="^4.1"
     - php: 7.2
       env: EXTRA_PACKAGES="doctrine/phpcr-bundle:^1.3 brianium/paratest:^1.0 doctrine/phpcr-odm:^1.3"
+  -   php: 7.3
+      env: SYMFONY_VERSION="^4.1"
   allow_failures:
     - php: 7.2
       env: SYMFONY_VERSION="dev-master"