travis-ci.org is a very handy service and integrates well with GitHub. Unfortunately there aren't ways to quickly check if your projects would build successfully other than committing and pushing to GitHub.
How to fiddle with Travis CI without pushing a gazillion of commits:
- fork a project, git clone it, optionally configure an "upstream" git remote
- create a branch for your changes
- do the changes, commit, push to your repo/branch and create a PR
- now you can make incremental changes: update the same commit with "--amend" and force-push with "git push -f". GitHub will update the PR and Travis CI will run again.
Committing with "--amend" and especially forcing push are very dangerous on regular branches. If unsure, use them only for this use case and remember to delete your branch once your PR has been accepted.