line chart に対応

対応しました
こんなかんじで

```html
<div data-petitchart="120,300,50,100,500,200,10,30,90" data-petitchart-type="line"></div>
<div data-petitchart="120,300,50,100,500,200,10,30,90" data-petitchart-color="blue" data-petitchart-width="320" data-petitchart-height="120" data-petitchart-type="line"></div>
```

で、こうです！↓

![2013-11-08 20 06 49](https://f.cloud.github.com/assets/29064/1499858/e4a22d22-4865-11e3-80a5-85952d9adda7.png)