How do I restart the Rails server after a code change for the changes to take effect?

Question

Ruby on Rails

Hello,
I am new to Rails and Ruby. I have my class in the lib folder, I make changes in the code, these changes are not applied, the changes occur only after the server is restarted. Thin server, run via rails -s.
Ruby 2.0, Rails 4.0.0, mine is in the environment in the console writes:

DEPRECATION WARNING: config.whiny_nils option is deprecated and no longer works. (called from block in <top (required)>
at ***/development.rb:10)
config.eager_load is set to nil. Please update your config/environments/*.rb files accordingly:
  * development - set it to false
  * test - set it to false (unless you use a tool that preloads your test environment)
  * production - set it to true