Issue title: How to use "csv-column-order" attribute?
 Issue body: An example would be highly appreciated.

Thanks,
Rahul
 Comments: 
 Comment 0: Hi,
You can define your html like this:
`<div ng-csv="testDelim" csv-column-order="order" filename="custom.csv"></div>`
In your JS file:
`$scope.testDelim = [ {a:1, b:2, c:3}, {a:4, b:5, c:6} ];
    $scope.order = [ 'b', 'a', 'c' ];`
It output:
`2,1,3  5,4,6`

 Comment 1: @shaohaolin  It doesnt seem to work as expected. Here is the relevant part of my code:

HTML:

```
<button 
    class="btn btn-default" 
    ng-csv="csv.csvArray" 
    field-separator="," 
    decimal-separator="."
    csv-column-order="order"
    csv-header="['URL', 'TITLE', 'META DESCRIPTION']"
    filename="{{ csv.filename }}.csv" >
        <span class="glyphicon glyphicon-download-alt" aria-hidden="true"></span>
</button>
```

JS:

```
$scope.order = ['link', 'snippet', 'title'];
// all other variables have valid data
// I am running this on Angular.js v1.4.5
```

 Comment 2: @shaohaolin I also tried it in jsFiddle and it wouldn't let me download the CSV. http://jsfiddle.net/HB7LU/18206/
 Comment 3: @rahul-desai3 You forgot to DI.
`angular
    .module('myApp',['ngSanitize', 'ngCsv'])`
 Comment 4: @shaohaolin I added that. It still didn't help :-|
 Comment 5: @rahul-desai3 Something wrong when you import the ng-csv file. Please update the latest.
Here is jsFiddle link that uses ng-csv cdnjs.
http://jsfiddle.net/HB7LU/18208/
 Comment 6: Updating it to the latest version works! Thanks @shaohaolin :)
 Comment 7: @rahul-desai3 You are welcome! Enjoy hacking!
{'source': 'GithubIssues', 'repo_name_with_owner': 'asafdav/ng-csv', 'issue_id': 110024604, 'repo_stars': 633.0}