Fixes #19: Add happiness as a third style option

[developit]

I like this module, but I use tabs and semicolons when writing ES6 - happiness is a fork of standard/semi-standard that enforces those rules out-of-the-box, so I figured it would make a good addition to this linter.

@ricardofbarros Apologies if I've messed anything up here - this is actually the first time I've tried submitting a PR to a CoffeeScript project :)

Edit: happiness issue: JedWatson/happiness#3

[ricardofbarros]

I will review this shortly, but at first glance everything seems fine, I need to start thinking on making tests.

[developit]

Yup, I was just going to ask if you had a way you normally tested this stuff. I've never hacked on an Atom package before, so I'm not sure if it's like npm where I can just swap the files locally or use link/link-local.

[ricardofbarros]

You can do the following:

• apm link linter-js-standard/ --dev
• atom --dev

I need to read more about the specs and how Atom does the unit tests, but that is how I test local stuff.

[developit]

I was able to confirm it works. On a project with tabs in-use, switching the engine from standard to happiness brought my error count from ~350 to ~90. Now I just need to fix up my codebase ;)

[dcousens]

LGTM thanks @developit :)

[ricardofbarros]

Merged :) going to release a minor version and edit the readme.

Thank you @developit