facebook/react — pull request #2490 by jquense (2014-11-08 21:56:04+00:00)
Title: Note the need for an Object.assign polyfill

Not sure if this is enough to just place it in the note. Or whether the MDN polyfill link is appropriate, I wanted to provide a solution along with the warning. Another option is pointing them to the react polyfil in the source...