Test travis config for PHP5 versions (#592)

* Run tests for PHP5.x
* Start from 5.3 since composer requires it and without it we cannot install phpunit
* Specify dist for 5.3
* Disabled nightly testing because phpunit doesn't support php8 yet.

.travis.yml

@@ -1,4 +1,3 @@
-
 language: php
 
 sudo: false
@@ -7,12 +6,17 @@ dist: trusty
 
 matrix:
   include:
+   - php: 5.3 # Composer requires PHP 5.3.2+ to run, so we cannot test below 5.3
+     dist: precise # PHP 5.3 is supported only on Precise.
+   - php: 5.4
+   - php: 5.5
+   - php: 5.6
    - php: 7.0
    - php: 7.1
    - php: 7.2
    - php: 7.3
    - php: 7.4
-   - php: nightly
+#   - php: nightly # PHP nightly build testing disabled because PHPUnit doesn't support PHP8 yet.
   fast_finish: true
   allow_failures:
    - php: nightly

CHANGELOG.md

@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- Travis unit tests now run for all php versions >= 5.3
+
 ### Fixed
 - PHP5.3 compatability fixes