warning code shows up in min build

[sophiebits]

See http://fb.me/react-0.9.0-rc1.min.js and search for "Invalid. We should either (a) change warning's implementation to warn only in __DEV__ and strip it in the build step or (b) change the callers to check __DEV__.

@cpojer?

[sophiebits]

(I think the functions that have the warnings aren't actually executed, but we should at least avoid including the warning message.)

[zpao]

I think we should just make warning look identical to invariant, then do the same thing we do in constants.js