no issue
- we had [previously reverted](787646a4a2) the use of `yarn` on Travis as we suspected it as being a culprit in failing editor builds, that wasn't the real cause so this switches us back to using `yarn`
no issue
- persisting the broccoli cache should dramatically speed up the client builds on Travis as it will only need to rebuild changed files and those that depend on them
no issue
- drop `jshint`, `jscs`, and `ember-suave` dependencies
- remove `grunt` related linting dependencies and tasks
- remove linting build from Travis so that linting can be performed as part of the normal test suite (refs TryGhost/Ghost#7427)
- add `ember-cli-eslint` and `eslint-plugin-ember-suave` dependencies
- configure `eslint` to match our previous coding style
- update config to run eslint tests as part of the normal test run
- add `npm run lint` command to only run linter tests
