To run a local copy of the site to see changes without pushing, install Ruby, Nodejs, and Bundler (for more info, see this GitHub Documentation):
curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash - # Add stable NodeJS repo
sudo apt install -y build-essential nodejs ruby ruby-dev zlib1g-dev # Install dev tools, NodeJS, Rudy, and zlib
sudo gem install bundler # Install Bundler to manage site dependencies
bundle install # Install gems to run Jekyll
Then run jekyll:
bundle exec jekyll serve # Run Jekyll with Bundler