Add examples to Travis

See #548 .
Instead of putting "tests" in the CI, I think we should put everything in examples for consistency. Ifthis get pulled I'll finnish the work with "tests".

The job is done by 2 bash lines in the .travis.yml to add them, as we should rely on "dub test" doing the biggest part of the job. This may not be the best way to do it, but it's better than what we used to have. Any advice / direction is welcome.

There are some examples that are build but not run:
daytime: Address specified is not correct + use a priviledged port;
mongodb: Needs a server
redis[-pubsub]: Needs a server;
sendmail: Needs a server
I don't think it's worth installing a mongodb / redis / smtp server on the CI machine just to test the driver, so there is no attempt to run them.