Long error messages should be cut in production

As noted by @blesh in https://twitter.com/BenLesh/status/727659194711597056, we should gate long error messages:

if (process.env.NODE_ENV === 'production') {
  throw new Error('short message');
} else {
  throw new Error('long message');
}

This way Uglify can dead-code eliminate the long version in the minified builds.

[gaearon]

The one important thing is to have consistent throwing behavior in dev and prod. Giving a shorter message in prod is fine, but throwing only in dev is problematic because it makes app behaves inconsistently.

[gaearon]

How it usually works: DefinePlugin/envify just replace process.env.NODE_ENV with a string. However it is Uglify that actually removes if ('production' !== 'production') blocks as dead code.