update heroku git remote code example

Example 1: git remote add heroku

heroku git:remote -a project

Example 2: heroku rename

heroku apps:remane --app <old-project-name> <new-project-name>

Example 3: rename heroku app

$ heroku apps:rename newname
Renaming oldname to newname... done
http://newname.herokuapp.com/ | [email protected]:newname.git
Git remote heroku updated

Example 4: git push to heroku

$ git push heroku master