On github, after I fork a project, modify it, then submit my pull request, it seems that I have to delete and re-fork in order to stay current with any changes made after my pul
You should add the original project as a remote to your working copy. Then you can pull changes from the original repository and push them to your forked repository. The commands for this look something like:
git remote add upstream <original repo url>
git pull upstream master
git push origin
What you can do is create a pull request in your forked repo by comparing to the original repository and then merge it in your repository.