I installed puma gem and when I start rails server by rails s I can see full output:
puma
rails s
$ rails s /Users/serj/.rvm/gems/ruby-2.2.1@email_
The logs are in log/.log. So you could (in a separate tab / window) run:
log/.log
tail -f log/development.log
And you'll see all your output. If you want the output from rails merged into the puma logs, you could always have rails log to STDOUT:
STDOUT
config.logger = Logger.new(STDOUT)