3.4/develop

Fully embraced the composer way of doing things, added requirement of PHP 5.4+, and added some fancy new 5.4 stuff.
@zombor :+1:  If someone wants to maintain a backport that's fine, but I think we should be going all in for PHP 5.4. A lot of things can be backported automagically (see [thomasbachem/php-short-array-syntax-converter](https://github.com/thomasbachem/php-short-array-syntax-converter)) if someone would like to maintain that.