Зачем эти файлы в 1.7.5

[Belena]

vendor/composer/installers/src/Composer/Installers/DrupalInstaller.php
vendor/composer/installers/src/Composer/Installers/CraftInstaller.php
vendor/composer/installers/src/Composer/Installers/SilverStripeInstaller.php
vendor/composer/installers/src/Composer/Installers/ShopwareInstaller.php
vendor/composer/installers/src/Composer/Installers/KirbyInstaller.php
vendor/composer/installers/src/Composer/Installers/TYPO3CmsInstaller.php
vendor/composer/installers/src/Composer/Installers/OctoberInstaller.php
vendor/composer/installers/src/Composer/Installers/MoodleInstaller.php
vendor/composer/installers/src/Composer/Installers/BaseInstaller.php
vendor/composer/installers/src/Composer/Installers/CakePHPInstaller.php
vendor/composer/installers/src/Composer/Installers/Concrete5Installer.php
vendor/composer/installers/src/Composer/Installers/OxidInstaller.php
vendor/composer/installers/src/Composer/Installers/BitrixInstaller.php
vendor/composer/installers/src/Composer/Installers/AsgardInstaller.php
vendor/composer/installers/src/Composer/Installers/WordPressInstaller.php
vendor/composer/installers/src/Composer/Installers/Installer.php
vendor/composer/installers/src/Composer/Installers/MediaWikiInstaller.php

[Adik]

Сторонняя библиотека это. В общем то она не нужна.  Больше для разработчиков, чтобы использовать Composer для установки prestashop.