Additional OPA data in tooltip

There's probably a way you can update your tile store to expose this data, but without recreating the map layer altogether there was no way for me to do that. Instead, i'm using the address information to query OPA via the web service at api.phillyaddress.com. This returns a boatload of information, and I've built a proof of concept to expose $ / sqft information on the tooltip.

Whether or not this pull request gets included in your repo or not, I think it's worth exposing additional data in the map layer one way or another.

![Screenshot 3:13:13 5:53 PM](https://f.cloud.github.com/assets/508451/256411/a8298e16-8c28-11e2-82e2-35e99fa2334a.png)
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