According to travis-ci/travis-ci#2111 and some own testing, it isn't possible to combine branch whitelists with tag-based auto deployment. Unfortunately it is necessary to whitelist the gh-pages branch, because Travis implicitly blacklists it.
Just adding some features inspired by other projects using Travis, e.g. a simple PHP syntax checker with various PHP versions. A short peak into @dav-m85 link leads me to think that running composer and creating the archive should be done with before_deploy rather than script.
