Updates .eslint.js to accommodate eslint 3.
Updates .eslint.js to accommodate eslint 3.

christianmemije/kolibri-exercise-perseus-plugin,christianmemije/kolibri-exercise-perseus-plugin,learningequality/kolibri-exercise-perseus-plugin,learningequality/kolibri-exercise-perseus-plugin,christianmemije/kolibri-exercise-perseus-plugin