feat(api): remove Api#setDefaultListener

BREAKING CHANGE: replace references to `Api#setDefaultListener` with Core#chainListener`

Author: bbartolome

lib/index.js

@@ -117,6 +117,4 @@ Api.prototype.view = require('./api/view')(_);
 Api.prototype.listen = require('./api/listen')(_, Core, WebSocketServer);
 Api.prototype.close = require('./api/close')();
 
-Api.prototype.setDefaultListener = Core.prototype.chainListener;
-
 module.exports = Api;