Removed Travis build for PHP 5.5 (no longer supported).

Author: Bilge

.travis.yml

@@ -6,11 +6,11 @@ sudo: false
 language: php
 
 php:
-  - 5.5
   - 5.6
   - 7.0
   - 7.1
   - 7.2
+  - 7.3
 
 matrix:
   fast_finish: true