travis CI

[DirtyF]

fix #106

[jenkoian]

Think we should build against latest stable and latest LTS https://docs.travis-ci.com/user/languages/javascript-with-nodejs/#Specifying-Node.js-versions

[jenkoian]

Thanks @DirtyF - a few bits of feedback:

• I think we should do this https://docs.travis-ci.com/user/languages/javascript-with-nodejs/#Caching-with-npm
• Should be using yarn, so think we should add this as well https://docs.travis-ci.com/user/languages/javascript-with-nodejs/#Caching-with-yarn

[jenkoian]

Now that #114 has been merged, would be good to add this as well 👍

[DirtyF]

@jenkoian addressed your feedback 😄

[jenkoian]

Thanks @DirtyF !