Building the library with grunt

Building now only requires `npm` via
```
npm install
```

I decided to bundle both vgl and geojs together into `dist/built/geo.min.js`.  All dependent libraries are bundled into `dist/built/geo.ext.min.js`.
The only purpose for this file is to build testing and to build the documentation.  For both of these things python is required.  That is why I moved it here.