Update metro.rake to use new importer
Update metro.rake to use new importer

This also adds the ability to import a single agency from a gtfs url:

`rake metro:import["http://url_to_gtfs_file.zip"]`
bus-detective/bus-detective,bus-detective/bus-detective,gaslight/bus-detective,gaslight/bus-detective,gaslight/bus-detective,gaslight/bus-detective,bus-detective/bus-detective,bus-detective/bus-detective