I cloned the repo at https://github.com/railstutorial/sample_app_rails_4 and made a lot of changes to it (I used it as a starting point for my own app), and now I would like to
Taken from Git push everything to new origin
basically you have to associate a new repo to your folder
git remote add origin <address>
git push origin <branchname>
Your purpose is probably to put this repo on yours and make it yours.
.git/
and re-initialize.
rm -rf .git
git init
git add .
git commit -m "your commit message"
git remote add origin
git push origin master