Implement promise support.

[marcodpt]

It would be interesting to explore the possibilities with promises and async/await.

• Plugins should be executed in order until the last one resolves.
• The done function from the previous route would be called and would have to wait until resolved.
• The new route action would be called.

This introduces some difficulties in case a promise is executing and a route change is triggered and it needs to be assessed how to proceed and test appropriately.