Convert large files to Topojson

It was noted in [this blog post](http://geosprocket.blogspot.com/2013/07/open-cadastral-data-github-test-case.html) that certain files [Burlington, for example](https://github.com/wboykinm/vcgi/blob/master/cadastral/vt_parcels_BURLINGTON.geojson), exceed to the 10MB blob limit. Not a problem.

These files, because of the number of arcs really lend themselves well to [topojson](https://github.com/mbostock/topojson/wiki), which can reduce file size by up to 80% in some cases (making the theoretically limit closer to 50MB per file).

This pull request converts Burlington, as an example of Topojson's capability to allow GitHub to serve large files. As geojson it was 10.8 MB. The file is now 3.1 MB and renders effortlessly on GitHub.

* [Before](https://github.com/wboykinm/vcgi/blob/master/cadastral/vt_parcels_BURLINGTON.geojson)
* [After (live map)](https://github.com/benbalter/vcgi/blob/topojson-example/cadastral/vt_parcels_BURLINGTON.topojson)

![screen shot 2013-07-25 at 3 44 55 pm](https://f.cloud.github.com/assets/282759/858280/b342bac2-f562-11e2-91b9-93386477da1c.png)

How to convert:

```console
$ topojson vt_parcels_BURLINGTON.geojson -p -o vt_parcels_BURLINGTON.geojson
$ git mv topojson vt_parcels_BURLINGTON.geojson topojson vt_parcels_BURLINGTON.topojson (optional)
$ git add .
$ git commit -m 'converting to topojson'
$ git push
```