directions lookup

Add a class/function to look up directions given the coordinates. Then use this class/function in a state to look up directions  for the user.
I think it might be easier to use `self.im.outbound`. Either that, or we'd need to do [the setting up step](https://github.com/praekelt/vumi-jssandbox-toolkit/blob/develop/lib/interaction_machine.js#L361-L364) that `OutboundHelper` needs.

Pretty awesome that you figured out how to use it without any examples though (we should probably make an example).