A simple bit of code to manage the concurrency of a function. Very useful in limiting the number of asynch calls in a loop.

npm install guvna
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Guvna allows for easily managing the number of times a function is run concurrently.

I ran into a problem where I neede to execute a resource intensive function iteratively and quickly killed the box.

To address the problem, I wrote the Guvna to govern the volume and execution of this function.

Version 0.0.5
Added the `this.percDone` metric to make it easy to show the percentage done in the callback.

Since Guvna now uses integer variables to signal when your callback has completed a run, you MUST include `;` in your function, though if you're running an asynch function, you'll likely have to create a reference to `this` as seen in the example below that gets tucked into the asynch function.  In the code below, I call create `self` so that I can get to the `.next()` function.

In this example, I use `setTimeout` to simulate an asynch call.

var	response = [],
		Guvna = require('guvna');

var guv = new Guvna({
	max: 2,
	list: [ { name: 'blargh' }, { name: 'honk' }, { name: 'toot' } ],
	callback: function(l) {
		var rand = Math.floor((Math.random()*10)+1) * 1000,
				self = this;
		setTimeout(function() {
			console.log(parseInt(self.percDone*100)+'% complete');; // CHANGE FROM v0.0.1
		}, rand);
	done: function() { console.log(response); }


When declaring your `guv` variable, you need to pass it several options:
* `list`: This is a simple array.  Each item in the array is passed to the `callback` function one at a time.
* `callback`: This is the function that you want to govern.  It is passed each item from the `list`.
* `done`: This is the function to run when all your `callback`s are complete.
* `max`: (optional) This is an integer for how many concurrent `callback`s you want to have running.  Default = `list.length`

* 0.0.5 - Added `percDone` metric.
* 0.0.4 - Added error handling.
* 0.0.3 - Tweaked calculation of `max` if it's omitted.
* 0.0.2 - Refactored to use tracking variables as using events created unnecessary comnplexity especially when nesting guvnas.
* 0.0.1 - Initial drop, used events to manage concurrency.
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