Implement CI in this buildout

[idgserpro]

After 7d9a64d we came to the conclusion that a CI here in Travis would be useful. The test can be really simple, like just testing if bin/instance exists after running buildout.

To avoid the prompt asking for user and password, the command bin/buildout instance:user=admin:admin can be used instead (or even better, this could be added to buildout.cfg itself but it's up to you).

[idgserpro]

FYI @thet

[thet]

sounds good!
I didn't know about the possibility of adding this instance parameters. We should do it so to keep the buildout really minimal and let the user choose which username and password to use.