Add php 7.3 build

sebastianfeldmann · sebastianfeldmann · commit 632ed1af2b6e · 2018-12-05T16:58:03.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -4,6 +4,7 @@ php:
   - 7.0
   - 7.1
   - 7.2
+  - 7.3
 
 before_script:
   - composer self-update
