We currently have a system set up so both Piwik core and plugins can be tested on Travis-CI. The system allows testing plugins against different Piwik versions and autoupdates so plugin builds are kept up to date. This unfortunately causes problems when testing against different versions of Piwik simultaneously. Older versions of Piwik will expect different behavior from the .travis.yml script, and this can't be changed from within a build.
To fix this, the travis system must be extracted into a separate repository. The repository will have branches/tags for each release of Piwik. In travis, the specific branch of the travis system will be checked out and the scripts run. This way the build will always function even as the travis system is changed. And we can patch older versions as needed.
Moving to 3.0 since the important pieces have been merged.