Ensure Rails responds to logger

[tily]

Summary

• Rails module will not always respond to logger
• OneLogin::RubySaml::Logging#logger should check if Rails redponds to logger before calling it

How to reproduce

$ cat Gemfile
source 'https://rubygems.org'
gem 'omniauth-saml'
gem 'kaminari-sinatra'

$ cat test.rb 
Bundler.require
logging = OneLogin::RubySaml::Logging
logging.logger

$ bundle install
$ bundle exec ruby test.rb
/usr/local/bundle/gems/ruby-saml-1.6.0/lib/onelogin/ruby-saml/logging.rb:10:in `logger': undefined method `logger' for Rails:Module (NoMethodError)
        from test.rb:3:in `<main>'