Why travis ci only work with Github

I am newbie to travis CI, i came to know travis ci will work with only Github, is that really true? Because source code can be anywhere now it can be in git, bitbucket, svn etc? is any reason only for Github now? Is any future plan to support other version control tools?

We integrate heavily with GitHub specific features, and are focused on delivering an excellent CI experience for folks using GitHub at this time.

It may be possible to set up mirroring between your git hosting service of choice and GitHub so that we can build your project, but this is largely theoretical and unsupported. (This may not be something you can do, either.)