Merge pull request #303 from pelias/OpenAddresses-License-Addition

OpenAddresses added to attribution under CC0

public/attribution.md

@@ -2,6 +2,6 @@
 * Geocoding by [Pelias](https://mapzen.com/pelias) from [Mapzen](https://mapzen.com)
 * Data from
    * [OpenStreetMap](http://www.openstreetmap.org/copyright) © OpenStreetMap contributors under [ODbL](http://opendatacommons.org/licenses/odbl/)
+   * [OpenAddresses](http://openaddresses.io) under a [Creative Commons Zero](https://github.com/openaddresses/openaddresses/blob/master/sources/LICENSE) public domain designation
    * [Quattroshapes](https://github.com/foursquare/quattroshapes/blob/master/LICENSE.md) under [CC-BY-2.0](https://creativecommons.org/licenses/by/2.0/)
    * [GeoNames](http://www.geonames.org/) under [CC-BY-3.0](https://creativecommons.org/licenses/by/2.0/)
-   * and other sources