🔖 Release 3.1

Merge pull request #7 from AlexHowansky/master

Fix PHPDoc references.

Merge pull request #4 from Ikstar/fix-php-74

Fix implode order of parameters

✨ Mark code blocks as being PHP (2)

Add `composer test`. Hat tip, @hannesvdvreken

Class Casing

Update README to showcase EL support

Don't eplicitly test PHP 5.4.0

(It's not available on Travis – travis-ci/travis-ci#516)

Rename Sgr.php to SGR.php

Rename Sgr to SGR