Travis integration

Issue https://jira.ez.no/browse/EZP-21167 is ready for review.

I have small doubts, though, about
"- make the test coverage available in the output" part of the issue.

Which output is that? 
Test coverage is shown here for each build:
https://travis-ci.org/ezsystems/ez-js-rest-client 
But nowhere else, I guess.
@dpobel : thanks beforehand for review.