now that we have GitHub Actions working, remove Travis CI

Author: chaimleib

.travis.yml

@@ -364,8 +364,8 @@ Licensed under the [Apache License, version 2.0][Apache].
 The source code for this project is at https://github.com/chaimleib/intervaltree
 
 
-[build status badge]: https://travis-ci.org/chaimleib/intervaltree.svg?branch=master
-[build status]: https://travis-ci.org/chaimleib/intervaltree
+[build status badge]: https://github.com/chaimleib/intervaltree/workflows/ci/badge.svg
+[build status]: https://github.com/chaimleib/intervaltree/actions
 [GH]: https://github.com/chaimleib/intervaltree
 [issue tracker]: https://github.com/chaimleib/intervaltree/issues
 [Konstantin intervaltree]: https://github.com/konstantint/PyIntervalTree