[split] PSR 7

PSR-7 https://github.com/php-fig/http-message
Maybe this is important.

Edit: http://www.php-fig.org/psr/psr-7/
Edit2: ZF3 has the intention to adopt this standard. Watch this video https://www.youtube.com/watch?v=B7aSNUa1rJo

I hope something like this gets implemented: https://twitter.com/lsmith/status/605366922536972288

@no1youknowz

I read the material you've pointed out and a fuzzy idea occurred to me. Maybe it could be possible an optional CI3-compatibility package (a CI3 API emulator) to be written. When it is installed, it could capture certain routes. The rest of the routes are to be served by CI4 code. Thus an application could be rewritten to CI4 gradually.