Pie as composer package

[thomas-0816]

It would be great to have pie available as a composer package.

e.g. https://packagist.org/packages/php-cs-fixer/shim provides the phar version of PHP CS Fixer, I think pie could be similar.

[asgrim]

Discussed before in #266 and #136 :

TLDR, conceptually you do not have a separate PIE version per PHP project. It does not make sense to do so. PIE is used to install extensions to a PHP installation, not to a PHP project.