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.
I think this is wrong; I think this should read `... proj4(code)`. `proj4.defs(code)` returns null

Not sure how I managed to miss this whilst testing yesterday :-(