Moved pipeline/sequence to lib/promise

refs #9178

- continue with killing our global utils folder
- i haven't found any better naming for lib/promise
- so, require single files for now
- instead of doing `promiseLib = require('../lib/promise')`
- we can optimise the requires later

ghost/promise/lib/pipeline.js

@@ -0,0 +1,31 @@
+/**
+ * # Pipeline Utility
+ *
+ * Based on pipeline.js from when.js:
+ * https://github.com/cujojs/when/blob/3.7.4/pipeline.js
+ */
+var Promise = require('bluebird');
+
+function pipeline(tasks /* initial arguments */) {
+    var args = Array.prototype.slice.call(arguments, 1),
+
+        runTask = function (task, args) {
+            // Self-optimizing function to run first task with multiple
+            // args using apply, but subsequent tasks via direct invocation
+            runTask = function (task, arg) {
+                return task(arg);
+            };
+
+            return task.apply(null, args);
+        };
+
+    // Resolve any promises for the arguments passed in first
+    return Promise.all(args).then(function (args) {
+        // Iterate through the tasks passing args from one into the next
+        return Promise.reduce(tasks, function (arg, task) {
+            return runTask(task, arg);
+        }, args);
+    });
+}
+
+module.exports = pipeline;

ghost/promise/lib/sequence.js

@@ -0,0 +1,17 @@
+var Promise = require('bluebird');
+
+/**
+ * expects an array of functions returning a promise
+ */
+function sequence(tasks /* Any Arguments */) {
+    var args = Array.prototype.slice.call(arguments, 1);
+
+    return Promise.reduce(tasks, function (results, task) {
+        return task.apply(this, args).then(function (result) {
+            results.push(result);
+            return results;
+        });
+    }, []);
+}
+
+module.exports = sequence;