Run tests automatically on TravisCI

[icemac]

Especially for pull requests it would be nice to run the tests automatically on travis-ci.org.

This requires:

• [x] To activate Travis-CI for this repository
• [x] Write a .travis.yml file.

After completing the first step (as it requires admin privileges in this repository) I can help with the second one.

[icemac]

@sorenroug What do you think about my suggestion?

[sorenroug]

@icemac I think it is a great idea to set up continuous integration, and I'll look into the practicalities in the weekend.

[sorenroug]

I have connected Travis-CI, but the build is currently failing.

[icemac]

Fixed #56.