Extended sequence utility

no issue

- support promise and none promise tasks
- helpful if you create an array of operations and not all of the operations/tasks are async
- `response instanceof Promise` does not work for all cases e.g. some usages return a transaction/bookshelf chain

ghost/promise/lib/sequence.js

@@ -1,16 +1,25 @@
-var Promise = require('bluebird');
+const Promise = require('bluebird');
 
 /**
  * expects an array of functions returning a promise
  */
 function sequence(tasks /* Any Arguments */) {
-    var args = Array.prototype.slice.call(arguments, 1);
+    const args = Array.prototype.slice.call(arguments, 1);
 
     return Promise.reduce(tasks, function (results, task) {
-        return task.apply(this, args).then(function (result) {
+        const response = task.apply(this, args);
+
+        if (response && response.then) {
+            return response.then(function (result) {
                 results.push(result);
                 return results;
             });
+        } else {
+            return Promise.resolve().then(() => {
+                results.push(response);
+                return results;
+            });
+        }
     }, []);
 }