logging initializer and gtfs_graph log function

[doublestranded]

Moving GTFSGraph log method into initializer for common use. This ensures both Rails and Sidekiq logging are done when appropriate.

[drewda]

@doublestranded your initializer looks good. One suggestion I do have is to expose the logger object, rather than just pass calls through to the info method. That would allow you to log at different levels (info, debug, warn) throughout the code. Easiest way to do this might be with alias_method: http://apidock.com/ruby/Module/alias_method