Add com.mapzen.open

Please review maintainer notes – there are two things to sort out:

Build pulls in a few dependencies – some from Maven Central, some from github repos, as well as some Android support libraries. One dependency – leyndo – is not found; it seems to have moved or disappeared. However, it's by the same author as the app itself, and the app's main repo has changed names, so it might be a dependency that is no longer needed. The only way to tell would be to try it out. In the meantime I've opened a ticket for this at https://github.com/mapzen/open/issues/356

Secondly, upstream does not seem to update its version information in AndroidManifest.xml. They do tag each release, but we may have to resort to forcing version codes and names. Not sure how to do this...