I've cloned this repository but I got two deprecation warnings:

Package guzzle/guzzle is abandoned, you should avoid using it. Use guzzlehttp/guzzle instead.
guzzle/guzzle suggests installing guzzlehttp/guzzle (Guzzle 5 has moved to a new package name. The package you have installed, Guzzle 3, is deprecated.)

Then I got another deprecation warning:

Package container-interop/container-interop is abandoned, you should avoid using it. Use psr/container instead.