Support rails STDOUT logging

Using this gem with a Rails Heroku app fails to initialize. Heroku require log to be output in STDOUT instead of using a file and doing otherwise throw an error on `open(path, "a")`.

This fix checks if the `RailsStdoutLogging` gem is used (Usually used with Heroku rails app) so the Rails initializer can create a STDOUT logdevice instead of using a file.