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.
Would you cherry-pick https://github.com/elemoine/ol3/commit/6524124a763a7185e948408f4a5b9cf65d786ff3 for more explanations on the use of a custom projection and custom transforms in this example?