[PR] Files built during build process should have a destination of build/x.x/

Previously, some files remained outside of the versioned directory system. These should exist separate from each other so that multiple versions can exist at once when necessary in production.

This also removes the declared `version` var at the top of `gruntfile.js` and uses `package.json` to specify `build_version` information when creating a build directory.

By having a `build_version` of something like 0.5, we're able to maintain smaller versions of 0.5.x to indicate revision while not causing a full URL change.