Added directions to map key block.
Replaced constants in User with configuration settings in config/initializers/bike_buddy.rb.
Moved geo methods out of User into new BikeBuddy::Geo module.
Moved Devise.mailer_sender setting to environments/production.rb, so all deployment-specific mail settings are in that config file.
In config/initializers/devise.rb, default Devise.mailer_sender to "postmaster@localhost".