2.2.0

• [FEATURE] add disabled property to lf-select prompt (#68)
• [FEATURE] add tabindex property to lf-textarea and lf-select (#67)
• [FEATURE] add support for ember-changeset (#64)
• [INTERNAL] upgrade to ember 2.15 & ember-cli 2.15 (#57)
• [INTERNAL] start using eslint-plugin-ember (#60)