Update hook.js

	trigger(){
		var args = arguments;
		var context = this.context;
		var promises = [];

		this.hooks.forEach(function(task) {
			var executing = task.apply(context, args);

			if(executing && typeof executing["then"] === "function") {
				// Task is a function that returns a promise
				promises.push(executing);
			}
			// Otherwise Task resolves immediately, add resolved promise with result
			promises.push(new Promise((resolve, reject) => {
				resolve(executing);
			}));
		});


		return Promise.all(promises);
	}

if the code blow should inelse block?

			// Otherwise Task resolves immediately, add resolved promise with result
			promises.push(new Promise((resolve, reject) => {
				resolve(executing);
			}));

From https://github.com/pagedjs/pagedjs/pull/23