Add a .travis.yml to use TravisCI for test builds

As I keep a copy of Kaffeine at github and it has integration
with TravisCI (with I use already on other projects), why not
add a target there to allow being notified in the case I screw up
with something?

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>