Out of memory using PHP defaults

[K.S.]

By default, at least for my installation of PHP, the memory_limit is set to 128M. @alcohol previously mentioned in #437 that "Composer (the core component of Satis) itself requires roughly 1gb to be available at least." This is almost true.

Composer actually manages the memory_limit itself to ensure it has enough memory to run (1.5G to be more exact).

I am requesting, as a feature/enhancement to satis, that like composer it should internally manage its memory requirements (as well as detecting OOM errors and pointing people to the aforementioned composer documentation).

Thank you.