Travis: removed unsupported PHP versions

Author: marc-mabe

.travis.yml

@@ -16,27 +16,14 @@ env:
 matrix:
   fast_finish: true
   include:
-    - php: 5.6
-      env:
-        - CODE_COVERAGE="1"
-    - php: 7.0
-      env:
-        - CODE_COVERAGE="1"
-        - PHPDOC="1"
-    - php: 7.1
-      env:
-        - CODE_COVERAGE="1"
     - php: 7.2
       env:
         - CODE_COVERAGE="1"
+        - PHPDOC="1"
     - php: 7.3
       env:
         - CODE_COVERAGE="1"
     - php: nightly
-
-    # HHVM is no longer supported on Ubuntu Precise. Please consider using Trusty with `dist: trusty`.
-    - php: hhvm
-      dist: trusty
   allow_failures:
     - php: nightly