Fail Safe Queue

It's a very simple Queue of functions. But also let's you define, for each one, a
rollback in case something goes wrong later on the queue stack calling.

Heavily inspired by caolan/async.

Installation

Quick Examples

__Success example:__
``js
var queue = require('fail-safe-queue')

queue([
{
up: function(next){
console.log('+ up! 1')
next(null, 1)
},
down: function(prev){
console.log('- down! 1')
prev()
}
},
function(next){
console.log('+ up! 2')
next(null, 2)
},
{
up: function(next){
console.log('+ up! 3')
next('3 con error', 3)
},
down: function(prev){
console.log('- down! 3')
prev()
}
}
], function(err, upResults, downResults){
console.log('err', err)
console.log('upResults', upResults)
})
`
__Will echo:__
`
+ up! 1
+ up! 2
+ up! 3
err null
results [ [ 1 ], [ 2 ], [ 3 ] ]
`


__Fail example:__
`js
var queue = require('fail-safe-queue')

queue([
{
up: function(next){
console.log('+ up! 1')
next(null, 1)
},
down: function(prev){
console.log('- down! 1')
prev()
}
},
{
up: function(next){
console.log('+ up! 2')
next('This method triggered an error :S', 2)
},
down: function(prev){
console.log('- down! 2')
prev()
}
},
{
up: function(next){
console.log('+ up! 3')
next(null, 3)
},
down: function(prev){
console.log('- down! 3')
prev()
}
}
], function(err, upResults){
console.log('err', err)
console.log('upResults', upResults)
})
`
__Will echo:__
`
+ up! 1
+ up! 2
- down! 1
err This method triggered an error :S
results [ [ 1 ] ]
`

API

$3

__Arguments__
* tasks - It's an array of tasks. Each task could be a simple function to be
called in order or an object with two functions, up: [Function(next)] and
down: [Function(prev)].
* callback(err, results) - An optional callback to run once all the functions
have completed. This function gets a results array containing all the result
arguments passed to the task` callbacks.