v2.3.1

• Fix display of section tags #102 @mansona
• Update Testing Setup #107 @aklkv
• Upgrade Ember #105 @aklkv
• Fixing Mascot Image on es-note component #90 @mansona
• Include trademark symbol on the Ember logo #96 @BradenLawrence
• Fix line height of headers #97 @underoot
• Export sass modules on ember-styleguide namespace #88 @ppcano
• Footer: separate data from the component #89 @ppcano