Set series options available on column chart

This code allows the user to add options on HighChart ColumnChart series (http://api.highcharts.com/highcharts#series), for example :

```
series: [
  {
    name: 'Serie 1',
    data: [1, 2, 3],
    yAxis: 0
  },
  {
    name: 'Serie 1',
    data: [1, 2, 3],
    yAxis: 1
  }
]
```

I've done it this way because it was the simplest way for me to add yAxis option on ColumnChart series.

Am I doing something wrong ? What do you think about it ?