add kernelspec for IPython 3.0

Still WIP, 

But once https://github.com/ipython/ipython/pull/6126 is merge this will allow to change running kernel in a single notebook server. This add the minimal changes necessary to register a new kernel with IPython.

The things that are still to figure out are the modification Julia bring to tooltip, and the logo/favicon that does not change (yet).

![capture decran 2014-07-26 a 22 43 23](https://cloud.githubusercontent.com/assets/335567/3712236/8a881e10-1505-11e4-8ecb-88739b503de0.png)

The idea is to provide a fallback value for any systems that might need a language name - like codemirror modes, pygments lexers, etc., given that we can't anticipate every such tool that might want to know what language it's dealing with. So there's no specific format, but I'd probably leave it in lower case.

I'm considering putting the mime type into the kernel spec as well, as a better specified generic identifier for the language.