Code linting

[sir-dunxalot]

This PR adds code linting to this addon using the following third-party code:

• ember-cli-eslint for the linting, which adds a test to the QUnit test suite for every JS file in the addon
• eslint-plugin-ember-suave, which adds the default eslint configuration and some custom rules designed for Ember
• eslint-plugin-netguru-ember, which adds some more custom rules designed for Ember

Where our preferred code conventions differs from the eslint plugins above, overriding configuration is defined in the .eslintrc.js file here.

The only rules I wanted to add that isn't yet supported are 1) enforcing empty lines before and after blocks and 2) enforcing empty lines before and after computed properties and methods. As such, I expect some PR reviews will still touch on issues on code conventions and styling.

You can see the eslint tests being run on Travis in this job.

[sir-dunxalot]

Fixes #151

[sir-dunxalot]

Removed because we don't use jshint anymore.

[sir-dunxalot]

Removed because we don't use jshint anymore.

[sir-dunxalot]

This file (full version here) is a good example of what code conventions we're actually enforcing. The conventions and rules are too numerous to list.

[a15n]

LGTM, did you make these changes manually or use a tool?

[sir-dunxalot]

Thank you. I thought about using the eslint --fix option but due to installation complications where I wanted to avoid installing eslint globally I opted to make all the changes manually.