Rails Localhost not working

So when I run "rails server" and try to open any project, i get this error when trying to open localhost:3000 : Error

But this is what my terminal says:

The thing is I thought it was because me pushing to git heroku was causing it to fail so another form said to uninstall heroku, however that didn't work and i still get this error.

$ rails s

=> Booting Puma
=> Rails 5.0.1 application starting in development on http://localhost:3000
=> Run `rails server -h` for more startup options
/Users/User/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.1/lib/active_support/core_ext/numeric/conversions.rb:138: warning: constant    ::Fixnum is deprecated
[27508] Puma starting in cluster mode...
[27508] * Version 3.7.0 (ruby 2.4.0-p0), codename: Snowy Sagebrush
[27508] * Min threads: 5, max threads: 5
[27508] * Environment: development
[27508] * Process workers: 2
[27508] * Preloading application
[27508] * Listening on tcp://0.0.0.0:3000
[27508] Use Ctrl-C to stop
[27508] - Worker 1 (pid: 27544) booted, phase: 0
[27508] - Worker 0 (pid: 27543) booted, phase: 0

Before, rails server would just stop at "Use Ctrl-C to stop" but it now has these worker id's and stuff. They probably happened when I installed heroku and tried to push my project with git heroku. What do those workers mean for future reference and how can I connect to localhost again?

What I've tried so far based on other stackexchange suggestions:

1. Uninstalling heroku
2. Deleting the heroku apps (these fail since they say there are no apps found even with the entire name used)
3. Commenting out the line "config.force_ssl = true" inside app/config/environments/production.rb
4. Deleting Procfile

Note: I've been following Michael Hartl's tutorial, specifically Chapter 7 http://ift.tt/1muevdZ And tried to do the SSL section and this is when I encountered errors.