Updated supported php versions in travis

Author: yannickroger

.travis.yml

@@ -1,11 +1,11 @@
 language: php
 
 php:
-  - 5.6
   - 7.0
   - 7.1
   - 7.2
-  - hhvm
+  - 7.3
+  - 7.4
   - nightly
 
 before_script:
@@ -17,4 +17,3 @@ script:
 matrix:
   allow_failures:
     - php: nightly
-    - php: hhvm