Fix PHPUnit version

`Error: Looks like you're using PHPUnit 4.8.36. WordPress requires at least PHPUnit 5.4 and is currently only compatible with PHPUnit up to 7.x.`

.gitlab-ci.yml

@@ -17,6 +17,8 @@ before_script:
   - |
     if [[ $(php -v) =~ "PHP 7." ]]; then
       composer global require "phpunit/phpunit=6.1.*"
+    elif [[ $(php -v) =~ "PHP 5.6" ]]; then
+      composer global require "phpunit/phpunit=5.4.*"
     else
       composer global require "phpunit/phpunit=4.8.*"
     fi

README.md

@@ -3,7 +3,7 @@
 **Donate link:** https://ethitter.com/donate/  
 **Tags:** latest, latest post, redirect, redirect latest, redirect post  
 **Requires at least:** 4.5  
-**Tested up to:** 5.4  
+**Tested up to:** 5.5  
 **Stable tag:** 0.3  
 **License:** GPLv2 or later  
 **License URI:** http://www.gnu.org/licenses/gpl-2.0.html  

readme.txt

@@ -3,7 +3,7 @@ Contributors: ethitter
 Donate link: https://ethitter.com/donate/
 Tags: latest, latest post, redirect, redirect latest, redirect post
 Requires at least: 4.5
-Tested up to: 5.4
+Tested up to: 5.5
 Stable tag: 0.3
 License: GPLv2 or later
 License URI: http://www.gnu.org/licenses/gpl-2.0.html