browser builds of React with addons are broken

996932d0423c9ca8f0b158065738b00e2a4cfeb1 breaks React with addons for System.js and the like.
The browser build of React with addons includes the addons in the same file, while in [the current config](https://github.com/goatslacker/alt/blob/996932d0423c9ca8f0b158065738b00e2a4cfeb1/dist.config.js#L22), it does a `require('react/addons')` which is incompatible.

Start with dist.config.js at line 22 and compare it with commit 996932d0423c9ca8f0b158065738b00e2a4cfeb1. Inspect how the browser build includes React addons for System.js and similar environments. Reproduce the browser build and verify that the generated file keeps the addons bundled without the incompatible require('react/addons').

Written by the indexing model from the issue text.