Add example on Readme to disable specific checks
Add example on Readme to disable specific checks

This was something that took me a few try-and-error cycles to get right, as the docs in `axe-core` are not very clear on the subject. Perhaps others find it useful.
ember-a11y/ember-a11y-testing,ember-a11y/ember-a11y-testing,ember-a11y/ember-a11y-testing,trentmwillis/ember-a11y-testing,trentmwillis/ember-a11y-testing