Adds fair queue

app/helper/queue/README

@@ -0,0 +1,46 @@
+Goal is to add a build queue which will cycle across all blogs with files to build.  I wanted to use another library like [bee](https://github.com/bee-queue/bee-queue), [kue](https://github.com/Automattic/kue) or  [bull](https://github.com/OptimalBits/bull) but I couldn't find one which would fairly distribute tasks across users/blogs/tenants. 
+
+For example, lets say there are three blogs: Alice, Bob and Chris. Alice syncs three files, immediately after Bob then syncs two files and Chris syncs one file. The fair build queue would process the files in this order:
+
+| Order | Blog | Task|
+|-------|-----|-----|
+|1 | Alice |        1st file|
+|2 | Bob |  1st file|
+|3 | Chris |  1st file|
+|4| Alice |        2nd file|
+|5 | Bob |  2nd file|
+|6 | Alice |     3rd file|
+
+The queue also needs to be reliable: 
+- the master process and any worker processes handling queue tasks can die
+- each task is processed at least once
+
+#### Example usage
+
+The api is copied from _bull_, though, which I liked.
+
+```js
+var Queue = require('queue');
+var queue = new Queue('build');
+
+var task = {can: 'be arbitrary object'};
+
+queue.add(blogID, task);
+
+queue.process(function(blogID, task, done){
+   // the function passed to process is invoked
+   // one at a time even if multiple items are queued
+   // call done to loop on to next task
+   done();
+});
+
+queue.add(blogID, {path: 'hello.txt'}, function(err){
+   // you can pass a callback for confirmation the task was added
+});
+
+queue.drain(function(blogID){
+   // called when all the tasks for a blog have been processed
+});
+```
+
+