Support for Skill Events

Adds SDK support for skill events

Skill developers now have the capability to integrate with Alexa skill events directly. If the skill is subscribed to these events, the skill is notified when an event occurs. Access to these events allows skill developers to build richer skill and external app experiences. A skill event is generated whenever a customer:

• enables or disables the skill
• links or unlinks a third-party account with the skill
• grants permissions to a skill
• changes the permissions grant to the skill

Echo show bugfix

• Fixing a bug in Speechlet response where having no shouldEndSession serializes
  to true instead of null

Support for Echo Show

Adds support for new Echo Show directives and Video

Dialog Management Support

Support for Dialog Management features is added