The free travis-ci.org service is going to be discontinued. The
replacement travis-ci.com could be used instead but is not exactly the
same.
The images provided by the service contained old kernel and this hinders
testing of new features, tests were failing and the coverage was
incomplete. The docker images will be used to do build coverage in
another way. A hosted CI is still desired so the search continues.
Issue: #171
Signed-off-by: David Sterba <dsterba@suse.com>