Change psi version, remove tile cachebuster

Two things:

- The `psi` module was updated six hours ago, and there's an error in the build. (See issue [here](https://github.com/addyosmani/psi/issues/30).) The `package.json` file has ambiguity with versions: `'*'` means pick the newest version of the module, which was causing errors. I just defined the version as `0.0.4`, which was the last clean build of `psi`.
- There was an error where `cacheBuster` was getting defined in a script tag in `reports.html` but not in `index.html`, so the map wasn't loading. (The map tiles definition had `cacheBuster` appended, but it wasn't defined.) I removed this -- we want the tiles to be cached so we don't make a zillion calls to Mapbox and CfA doesn't get charged for each request.

This should make everything awesome! Once merged, just do an `npm install` and everything should work. :smiley_cat: