[io.js] Print a warning message if the user is not on io.js 2.x

Summary:
Detects if the user is on Node or io.js 1.x and prints a banner explaining how to upgrade. We probably should link to more detailed upgrade docs so this is just a start.

I also added a function to format banners that is kind of useful.

Addresses part of #1737

![packager-banner](https://cloud.githubusercontent.com/assets/379606/8447050/ad615402-1f67-11e5-8c02-ece5f7488135.png)

Closes https://github.com/facebook/react-native/pull/1824
Github Author: James Ide <[email protected]>