Use the new proj4.js

This change updates ol3 to work with the new [proj4.js](https://github.com/proj4js/proj4js). Proj4js versions < 2.2 are no longer supported.
My editor's linter complains that these functions are used before they are defined. We could move them at the beginning of the file but this will make the example's code harder to read and understand. So let's keep them here. My eyes will bleed each time I open this file but I guess it's ok :-)