adds automated versioning of files

Hiya,

I noticed the version number in `bower.json` was trailing behind, so I added automated versioning with `grunt-version`.
There's a `version.json` file in the root of the project now, in which you declare which version number to use. The grunt-version task automatically replaces the version numbers in all the files as configured in `Gruntfile.js`.

There is one change to the source itself too. I removed the version number from the comments and stuck it into a `Geppetto.version` member, otherwise grunt-version couldn't recognize and update it. Hope that's ok.

If you get sick and tired of me meddling with your lib just let me know :grin:

Oh, and I didn't bump the version number.