Composer autoloading doesn't include CMB2

[bignall]

With the current version of CMB2, composer autoloading isn't supported (e.g. there's no autoload in CMB2's composer.json)

I've submitted a PR to CMB2 to fix that, but meanwhile you have to require CMB2's init.php by hand or add autoload to composer.json yourself.

[dmhendricks]

I agree that this would be a convenient change. Carbon Fields already supports this.