add directions link

This'll need a new location/styling once the map is properly displayed. iOS map links direction taken from https://developer.apple.com/library/ios/featuredarticles/iPhoneURLScheme_Reference/MapLinks/MapLinks.html#//apple_ref/doc/uid/TP40007899-CH5-SW1.
Merge pull request #15 from carpeliam/screens

add directions link