add travis support

Right now travis only supports precise, which doesn't have a new enough kernel
for us to actually run lxd. Thus, we just die if `go fmt` reports anything or
if the build fails.

Once travis fixes https://github.com/travis-ci/travis-ci/issues/2046 we can
actually run lxd and do some container creation and things.

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>