Setup Travis

[erikvold]

Running the tests on travis will help ensure that regressions do not occur and make it easier to contribute (since travis will display if the pull request tests pass or not in the pull request).

[jcranmer]

I'd love to have automatic CI builds for JSMime. Unfortunately, it doesn't work in node.js yet (since v8 is somewhat behind in implementing ES6 features and node.js even more so), which means the most reliable tests are via chai in the web browser, the automation of which is beyond me.

[erikvold]

@jcranmer I think I can hack this together, I've got firefox add-on tests running on nightlies in travis builds for a few add-ons now already.

[jcranmer]

Sorry for the late response. If you can set this up (or already have done so), I would be happy to see it in place.

[lygstate]

Now it's possible to setup the CI build for jsmime now, cause gulp test could be able do the test, along with the coverage