Spec action allow multiple callbacks

[chafnan]

It would be nice if the the action would allow multiple callbacks.

For example, in express you can create a route like this: app.VERB(path, [callback...], callback)

It would be nice to be able to chain the callbacks in a similar way. This would allow for using the route in the same way as express.

[mgutz]

see #132

[fehguy]

This is handled in #209